Higher temperature? I have squeezed the bag during BIAB pretty aggressively and haven't extracted any tannins (that I can perceive).
It's a misconception. You certainly can squeeze the grain bag you use for steeping. Tannin extraction is mainly dependent on pH, so if your pH is OK there shouldn't be a problem. Keep in mind that grain will drop the pH of your water, but of you use too much water for steeping the grain won't be able to drop it enough and you may get tannins.