I can see that If it's a solid wood nitro acoustic, I would DEFINITELY wait. I could wait an extra day for that.
An electric, I never have before and never had a problem, but 24 hours of wait worth is not having a problem to me. Never totally thought about it tbh. But IF something were to happen, I would regret it. As far as voiding the warranty, that's bullshit IMO.
But 24 hours is to me worth avoiding a headache. TBH in the future I will reconsider.