This strategy fails for appointments during that hour where the clock goes back: they are ambiguous, can refer to two different moments in time.
That caveat aside: good.
Sounds like the quoted RFC would help here. Storing the offset would make it unambiguous which of the two moments was meant. Your business logic would have to figure out what to do when the offset no longer exists (honour the clock time or convert to the new timezone) or is nonsense. The geographical reference would help decide what to do if you're not in a single location.
Humans would often fail such appointments too.
I have yet to find a technological solution to this social problem.
Also, I have yet to encounter this problem. For personal events, I sleep during this time. For company events, we always avoid this time.