If he got a warning, then that's the end of it. Foe is likely singing sour grapes because he's not good enough to beat players ranked ahead of him. He has a difficult time w/ folks ranked below him as it is
According to the NYT, he got a warning. And, in that case, Tiafoe was wrong to say "nothing happened," so then he does mean maybe he should have been defaulted. It seemed like a lot of nothing.
But a couple of years ago, if you remember, doubles player Miyu Kato and her partner were defaulted after Kato accidentally hit a ball kid in the neck when returning a ball to her — not even swatting it in frustration. They originally got a warning, but the other team complained, and the got defaulted. That, to me, seems a total misreading of the rule. Some years back, Roger did the same thing...hit a ball kid when trying to, helpfully, nudge the ball towards him with his racquet. Roger apologized and petted him on his head, and they moved on. Someone needs to clarify this rule to the umpires. I think they should rewrite it for clarity.