Just curious, how do you know that (a) you failed in HR (b) that it was this question and (c) for this reason?
I ask because it's unlikely that this was literally the feedback given you. Also, "I work too hard" does sound a bit canned.
>> The technical interviews, 6 of them in a row!, felt more like they were wanting to see me fail spectacularly rather than focus on my approach of solving whiteboard problems.
I do think this is more "in your head" that real. Nobody shows up to an interview wanting the other person to fail, but "how they solve whiteboard problems" isn't the goal either. It's more about - how does the person, think, collaborate, make tradeoffs and drives to an outcome - the goal being specifically to translate that outside the whiteboard space.