To be fair, I dont think it's a humblebrag. If they worked at the same company as all of us, it might make sense to call it a humblebrag but, there are enough people around here in much better positions than those that get bonuses like these for it to make sense to brag about. That is, I (and probably most people on yc) would feel embarrassed talking about my best accolades when there are people on here that were able to retire by 30, work with Freeman Dyson, or found some successful company.
I think they just used themselves as an example to provide the support that their argument wasn't coming from someone who values doing the bare minimum (which I've seen argued on yc a few times).