I suppose in theory the maintenance closure could be Sunday night and early hours of Monday instead of Saturday night. But if that is practical is a different question.
However recently TfL have been changing (reduced) some night bus frequencies on Friday and Saturday to match other nights, so not sure if they have changed policy on providing a night service in recent months (the PR spin only highlights improvements and is very quiet on reductions).
But of course these policies ebb and flow depending on how much money the mayor wants to spend, as an example at one time was going to be hourly night service around Kingston loop (and that had same problem discussed here about when is maintenance done).
My limited observation suggests nowadays Friday mornings can be quietest loadings (possibly less than Sunday morning), but I don’t want to go too far off topic whilst discussing passenger flows.