If anything it’ll be below 100 due to altitude. For example salt water for making pasta boils still at approx 100 deg. C. It takes quite a lot of salt (way more than you would ever want to consume) to meaningfully raise the boiling point.

You must be at altitude. That definitely makes a difference for the boiling point, but of course water freezes at 0. Impurities that you’ll encounter in tap water, for example, will not have a large effect on freezing point.

Even if it was different by a few degrees, how does that make the scale any less intuitive?

I don’t know what high school you went to, but we sure as shit didn’t cover stuff like partial differential equations and functional analysis.

Not at all. People (engineers?) seem to forget that experimental physicists exist

What of experimental physicists?