Does poking steaks and other meats cause flavor loss?
This is totally fine. Meat gets poked and prodded all the time, whether to test it, to pick it up with tongs, or sticking a fork in it to cut. Meat just is not that fragile.

Things like smashing with a tenderizer are much more violent and do affect the texture (that's kind of the point), so that's not a great comparison. But this is a really minor thing.