I don't think there's much you can do to get more fruiting tips beyond favoring weaker wood. Newtown is not a tip bearer in the true sense anyway as it bears fruit from spurs on two and three year wood more than from tips, IME. Some varieties like Yellow Transparent bear primarily from the tips of one year shoots but it doesn't require any special pruning technique to get ample crops.

What rootstock are we talking about?

I don't remember the specific rootstock and Grandpas shuts down their internet catalog in the off season to refresh my memory. I want to say m111. Possibly b118. I'm as sure as I can be that it's one of those two and not a G.

So far it hasn't tried to have a spur but it has only had 2 bearing years to show me. It has only been the tips that produced flowers both years.
My niece's on semi-dwarf in my yard has put out things that look like spurs but hasn't had a flower to confirm. That would be an interesting twist if my niece's grows more like Newtown and the one I bought as Newtown doesn't.
The reason I'm not sure about my niece's is the flavor from her yard was extremely tart and the Newtowns in my yard weren't. I'm hopeful I can do a side by side from the same yard next year.

So if I prune the Grandpa's tree like I was trying to encourage spurs next year that should cover it for however it's going to bear? And my idea of pruning back the whips as I pick the fruit this year might be a good start at that (it'd be late but I think too late to get any growth from pruning).

Lodi was easy to figure out with the fruit being off the tree in July. I just tipped everything after fruiting and it had plenty of time to set up flowers for next year. I've got it bearing away from the tips. At least I did before fireblight took out a bunch of spurs this year.

I'm surprised pruning back the "whips" would work for you. Generally any cutting back discourages fruiting except when done a few times during the growing season to individual annual shoots. Some varieties apparently respond by becoming fruiting spurs with this treatment- as we discussed earlier, it seems Macintosh does not.

On my Newtown, all the apples on the tree are on spurs below last year wood- I just checked it out. They will not be ripe until almost Nov..

The late August pruning worked on my regular McIntosh to get it fruiting again.
This tree does have a similar fruiting growth to it. That should be OK if it is like regular McIntosh because left alone that McIntosh uses spurs and this Newtown is planted in a spot where it can be left alone.

But,
I was just out and the Newtown might have flower buds down the branches set up to be spurs. It might be be ready to start producing next year. I'll leave it alone one more year.
Or if they're not flower buds I'll tip the branches without fruit sometime late next summer. Either turn them into spurs or try to get as many tips as I can.