It's not 11 games. It's just 11 quarters. Just 88 minutes. It's like judging a player halfway through their 3rd game, way too little information to go on.
Two years ago Beal shot 52% in the 4th quarter and 40% from three over 70 games. Those are incredible numbers. Last year he shot 45% over 52 games, still decent. That suggests that the issue is simply a tiny sample size and not that he has some random new problem in the 4th (unless adding Russ means that Russ is hogging the rock in the 4th and not letting Beal get the ball in good spots). Do you really think, based on that 11 quarter sample size, that Beal in his 9th season suddenly became a 4th-quarter choker in some meaningless early regular season games?
I mean right now Jimmy Butler is shooting just 30% in the 4th and Kemba just 22% in the 4th, if you want to point out how silly small sample sizes can get you. On the other hand, Bam, Christian Wood, and Colin Sexton are all shooting over 60% in the fourth. All those numbers are going to regress to the middle eventually.