There are many gurus here who know more than I do, but from what I've read, I think that should be fine.

If you can, mark off 42in from your current work area and see if you have enough room to move around. Most things I've read say a minimum of 36, with 42 being preferred, and 48in if you have chairs. This 48 may apply to high traffic areas as well, but since you're only talking about 18in long, it's not going to be that often that it gets that tight (like when two people pass in that 18 in at the same time.)

I'd hate to see you lose the functionality you've built in to your island.

I'd mark it off on your floors with tape to see how it feels for a few days if you can.

Question, are two people often working together in the clean-up space?
If so, I would want more space on that side.

I don't think we hae any aisles in our kitchen that are wider than 42, and that includes the final size around the eating area of the island. But, if I could increase the size of the aisles, I would do it on the working sides of the island.

It sounds like you gave this a lot of thought when you made the original measurement decisions. You don't say what your prep aisle will measure. I chose to have a larger traffic aisle then clean up aisle and don't regret it. Like you, all traffic funnels through here and it is where people greet when we entertain.You don't give the length and width of you island so it's hard to say if gaining that 9" inches by shortening the island is a good option. My prep aisle is intentional 42" not 45" and I find it comfortable for two workers but we are slight, small people. I wanted those extra 3" in a traffic aisle that contains a slice of 22" of island seating.

Think about what you have now and how it works (or does not work) and you will make a good decision for your lifestyle. There is no one right answer here. Look at the big picture since this traffic aisle is involved.

The prep and cooking aisle is a full 48 inches after countertop and range clearances. The cabinetry of the island is 81 inches while the countertop will be 83. The prep space to the left will remain the same (47.5 inches) if I shorten it. It is the space to the right of the prep sink that will change. If I put the sink and the trash in a 33 inch cabinet, I will gain 9 inches of aisle space and reduce the counter to the right of the sink to 8.5 inches. If I use a 36 inch cabinet, I will only gain 6 inches of aisle space but will reduce the space to the right of the sink to 11.5 inches. Currently with the 27 inch sink base and 12 inch trash pull out, I will have 14.5 inches to the right. For what it's worth, the prep sink I'm using will have a prep ledge integrated into it so I'm not too worried about losing the space to the right.

45" is way too narrow for a major passage way. 60" is reommended and you aren't even close. Your working aisle is fine, or even a bit large for some.

We have major hallways narrower than 45" so I don't think having that for an 18" section is at all bad. It sounds like you thought this out well from the beginning and will be fine.

In a public library, strangers have 48" aisle space to walk past each other, and they are surrounded by very tall book shelves that are worse than walls because you don't want to brush against the books or snag on the shelves.

If I understand this, the 45" width space is only for 18" and then gets wider.
This involves one step, or a half of one.
Any two people can walk past each other easily.
Even a long corridor can be less than 45" wide and often is.
Norms may have been printed, for ideals, for situations other than yours;
but I think they are irrelevant to your situation.

I, for one, think that the guidelines for aisle clearances are way bigger than are necessary in most normal homes and, in some cases, way bigger than desirable.

I was warned that the 42" in my main work aisle (prep, cooking, clean-up) would be "FAR too small for two people to work comfortably." In three years, my husband and I have yet to bump butts in that aisle (at least not accidentally!), and although we are not huge people, our butts do take up considerable space. If I had it to do again, I'd make that aisle narrower not wider! I do almost all my prep at the island, and I'd love to be able to just pivot to my stove. As it is, it's a pivot and a step. Not a big deal, but I certainly wouldn't want it to me more space than that!

I was also warned that 47" would not be enough space for my main traffic aisle through the kitchen, because I had pantry cabs opening into the aisle on one side, and island seating on the other. Never once in three years has this aisle seemed too narrow. We have very large parties quite often, and never once has that area seemed cramped.

What you describe seems like you have perfectly reasonable clearances. Unless there's something I'm not picturing correctly (a drawing would help), you should be just fine.

I think your spaces sound fine as you've made them. My butler's pantry is a couple of inches narrower than your pinch point, and considerably longer. The upper cabinets are the same depth as the lowers, and there's only a counter on the one side. It's the tightest space I have. And when several fairly large people are walking back and forth to the dining room serving there's really no trouble passing.

I don't remember your floorplan, if I've seen it. One thing to keep in mind is that people will naturally pool in the widest areas. Therefore, widening the area where you don't want people would be a mistake.