Then it sounds like Firefox has the "restart page" to mitigate this exact edge case. Better than having undefined behavior like that imo.
As I get it from other comments, this is not a problem with the built-in updater (as on Windows). On linux, when updating via package manager, you should now this can be an issue with any program. Yes, most programs survive running while being updated, but for a complicated piece of software (like a browser) this behavior is understandable.
I don't think anyone has the need to check such a message for grammar or spelling mistakes.
Even then, I would not rely on a LLM to accurately track this "evolution of language".
> Won't this also forbid virus scanners that quarantine files?
Yes. If I really _want_ to execute malware on my device, I should be allowed to do so by disabling the antivirus or disregarding a warning.
> I don't think it's reasonable to expect any manufacturer to uphold a warranty if making unlimited changes to the system is permitted
It is very reasonable and already the rule of law in "sane" jurisdictions, that manufacturer and mandated warranties are not touched by unrelated, reversable modifications to both hard- and software.