You still have to do some post-processing work around NB, since you’ll often end up with non-aligned pixel blocks, much higher color depth, and so on.

I actually did some testing of spritesheeting with Nano Banana Pro a while back:

https://mordenstar.com/other/nb-sprites

If you use the editing capabilities and send in a grid of 32×32 cells on a 1024×1024 image, you can get it to flood-fill in each square, so you end up with properly aligned 32×32 tiles. Then you can squash it via nearest neighbor to pull the lines back out, and reduce the palette using something like unfake.js:

https://github.com/jenissimo/unfake.js

Exactly! On my tool I specifically use 4x4 grids which is limiting and I use canny edge maps to help enforce consistency. A very fun problem to solve!