First of all I agree that it's no big deal. But it's also a nice convenience feature; I'm pretty happy that my computer works for me automatically.

Then to reply to your points. I don't use a VPN, but I regularly travel between south-western Europe and north-eastern Europe. The timezone is CET everywhere, but the actual solar time differs by about 2 hours. It may be a niche case for you, but can't I enjoy that it just works (for now)?

(Reasonable people may also disagree that traveling with your laptop with night colors is an "extremely obscure use case". It's a builtin feature on KDE. The night time also depends on the latitude which is not something captured by the timezone)