The point is that by making it seem as though being rejected by YC is a valid reason to start looking for a job misses out on the fact that YC is limiting the number of applicants that they will accept for a particular batch.
You could be very good, very viable and succeed with or without YC funding (because, for instance you could get funding elsewhere or because you bootstrap your way in to a success). Without YC spending a lot more time on their rejection emails (and I agree that their current rejection letters are as good as they could be without opening the door to a lot of discussion) you can not know what their reason was, and especially the more viable ones might be hit at a time when they are vulnerable (just after being rejected).
Job postings should be level headed and not single out people that have just been kicked in the nuts at a moment when they're vulnerable by targeting them directly.
That's putting the other party at a significant disadvantage.
You could be very good, very viable and succeed with or without YC funding (because, for instance you could get funding elsewhere or because you bootstrap your way in to a success). Without YC spending a lot more time on their rejection emails (and I agree that their current rejection letters are as good as they could be without opening the door to a lot of discussion) you can not know what their reason was, and especially the more viable ones might be hit at a time when they are vulnerable (just after being rejected).
Job postings should be level headed and not single out people that have just been kicked in the nuts at a moment when they're vulnerable by targeting them directly.
That's putting the other party at a significant disadvantage.