Does protection exist at all, today? I think it has to, logically.
Teams today don't think about "protection" at all but they do think and act in terms of "expected results" and they model out "expected results" for their own players and their opponents and iterate constantly to try to perform actions that have the lowest possible "expected results" for their opponents.
Sometimes this means pitching around hitter A to pitch to hitter B. You would do this if the expected run value of hitter A hitting against you is say 1 run but the expected value of hitter B, hitting after hitter A has walked, is 0.8 runs. This is based on their projected wOBA and run matrices.
Obviously, if the difference in talent between hitter A and hitter B is large, you would see this type of action by opponents more often.
So it stands to basic reason that if Hitter A benefits from having a Hitter B behind him who is just as good, that Hitter A will not suffer these slight reductions in his production by having the chance to hit essentially taken away from him. Like, if they pitch around him he gets credit for 0.1 runs for the walk, but maybe his "expected" production if pitched to is 0.2 runs - this means if he gets pitched to all the time in these scenarios over the course of a season his wOBA will literally be higher!
We have just proven that protection exists, on first principles!