Updating from one version of J! to another is normally a 10-minute operation (even if you have to update in stages). Certainly, in a few
cases we've seen over the past decade, some
people have problems; most people don't have problems. Whenever I update from one version of J! to another I do not set Protostar
as the default template and disable all third-party extensions. I update J! websites all the time.
The documented procedure is not a "one size fits all"; it's the recommended procedure as the first thing people should do.
Are the other preparatory steps, like setting Protostar
as the default template and disabling every third-party extension installed on the website, a case of "overkill"? Possibly. Is this a case of being overly-pessimistic? I think so. Are these kinds of instructions confusing to people? Absolutely!
Let's keep things simple and stay clear of "expert panel discussions". Instead of guessing and anticipating the worst-case scenario, let's allow the OP to use the Joomla! Update
procedure as it was intended to be used, hmm?