Can I do a 10lb pork loin in the Instapot?

Sure. If it will fit you can "do" one. But what are you shooting for, shredded pork? Pork loin doesn't hold up that well in a instpot if you're wanting sliced pork.

I had to jam a 10 lb. but in and that was after deboning, trimming, and using my Tetris skills to section it so it would fit.

But that was for Kaluah (pulled) pork. As was said above, cooking it for slicing would be difficult to say the least.

There is so more variability with an Instapot. There’s really no way to cook something to a desired temp.