What is the back story here?

Looks like topping to me which is generally a bad idea.

Again, what is the tree and what is the situation?

Oh, "B" is less bad than "A". Still probably a wound a mature tree will never encapsulate.

I wouldn't stress over it. When actually looking at the plant, a cleavage plane can sometimes be seen and followed but the tree can handle either equally well. Size of wound-not indicated here-is the essential factor-can the tree close so big a wound? And we don't know from this sketch what size wound we're talking about here.

what they said as to topping ...

when i have to make similar cuts.. not in topping.. it kinda depends on how you can get the saw in there ... if you can at all ... and double it all.. if its a chainsaw rather than a tree saw ...

look at B .. you cant come down from the top .. and often you cant come up from below ...

ken

I see a third option. Look at the original diagram.....see the small branch emerging from the left at the top of the central leader? I would make the cut to that outward growing branch.

I'm not discussing where or whether or not to make a given pruning cut, whether to top trees or not (don't) or any of that. I was simply commenting on the OP's perceived questioning as to angle of cut. That's largely immaterial.

B. If it is not more than 1.5" (give or take) diameter, I'd use a lopper. Much more precise and less likely to damage nearby branches. May I ask why you'd remove the leader?

Drop crotch. Not topping. It is the drawing that is "truncated",
in the interest of space and of intended focus on the question.

I would think that the answer (A or B or doesn't matter)
would be generally applicable, not diameter-specific.

No obsession on my part.
Simple question, simple answer,
any complexities were tacked on.

Hence, my use of the word "we" in my earlier post.

I am not sure why you need to do this, I would like more in depth information. Also, this wouldn't be the time to do it because any new growth wouldn't have a chance to harden off. Wait until spring.

Thanks, I'll wait 'til spring.

Why reduce height? So that I do not have to
climb so high to retrieve the cat.

Sounds like a leash would be an easier fix. Letting it loose could be a legality issue, as well as being immoral. Hope you take that into consideration, the tree will grow. Check with your municipality and/or HOA (if applicable).