At what point is upper body training detrimental?

I know there is no limit to strength (becoming detrimental) but in general, is doing too much upper body training going to be bad for a sprinter? The benching, curls, and isolation exercises and all that.
Is it only bad when someone starts becoming a “bodybuilder” and gains too much upper body mass? In their pecs, lats, etc. ?

You haven’t even come close to the point where size would be a problem, if that’s what you’re trying to get at (based on the other info you’ve posted here and on ET).

As discussed here numerous times, some of the biggest issues would occur when someone is training to such an extent it begins to inhibit their ROM around the shoulder (and would likely be causing related tightness in their upper back and neck). This is not necessarily a size or strength specific problem, but from poorly programmed training, which is what would happen if someone’s upper body began becoming detrimental. The would be the first issue to really look at, along with obviously any issues of the upper body training interfering energetically or “neurally” with the training of the sport (sprinting). A much distant second in my opinion would be any size issues. I say this because by the time someone got to the point where the size was actually causing significant problems or problems worth addressing, there would have already been red flags with these other issues.

One way this could be avoided is obviously ditching some or all of the isolation exercises (ie curls, tricep extensions, and the like) and then any hypertrophy would be a bit more isolated to important areas. It would still though take a while for this to become and issue and almost assuredly would be diet related (can’t gain muscle if you aren’t eating excess calories). At your size, strength and speed, it isn’t even worth thinking about.

Im just wondering in general, I see really well muscled sprinters and just makes me wonder how much more size they can afford to gain. But ya the decreased ROM is what I thought about too.