Does the beef cut matter when making stroganoff?
Beef cut does matter. Sirloin tip is a relatively tender cut, cuts that have done more work like shoulder, round, leg cuts have more connective tissue and need a significantly longer cooking time. In a pressure cooker this isn't that long, 1 hour is what I've seen for instant pot recipes using working cuts. 

Also what matters is fat content. Whatever you put in the instant pot is going to come out of it, if you put a fatty cut in you'll have a fatty result, so think about trimming. 

I would fry a portion of one of the steaks and see how tender the result is, that's a good gauge. Plus you get to eat steak.