This is individual. Some get by with less sleep than others. Also, consistency/doing it long term with all the general things matters more than being obsessed with one thing or another
If I've had loads of short sleeps in a row, it soon catches up with me (usually the week after)...and especially if I've been blasting balls to the wall in the gym.
If you struggle with every ounce of gains, I'd say get as much sleep as possible (a good routine is probably more important than exactly how many hours though). Your sleep cycle/hormone cycle adapts to a certain degree (to how you've been sleeping), so getting to bed before 10pm would be good so long as it's a routine.