Otherwise, I'd never dare to do something like that.
Its also a legal nightmare for the hoster if something goes wrong.
How do people on the Internet come to such random conclusions when there is no way you could have known the full terms of the contract between the author and their client?
Yes. I also always let my customers sign off when I change the libraries I use. Completely sane approach.
The major providers such as GCP, AWS etc share very few details about their underlying infrastructure with their customers. They change all sorts of things all the time.
As has been said, it varies case-by-case, and the OP believes they have a relationship with their client such that they didn’t need to provide notice for this, and they’re probably right. But most people doing this would send out a “maintenance is occurring on this date and some downtime may occur” email.