Bus factor 1 is rarely enough for "entire business". But if the GPUs are for training models, and their users are the data scientists that are also on holiday around the same times - that might indeed be good enough policy.
Ouch, that is indeed a risk one must be wary of. Can be a "works for the company but sucks for employees". Which can also drain the company of skilled people, a poor trade in most cases.
I’ve seen this before. It turns into restrictions on when you can schedule vacation times.
Not fun when your family wants to go on a trip but you can’t get the time off because it’s not one of the allowed vacation times.