Interesting. In Germany I've always had the opposite issue of my superiors vastly preferring I used "du" for them instead of "sie". I've always had some trouble with that since in Russia you usually try to address senior employees, your teachers and professors formally, although tech companies are as usual a big exception.

Many people were quite unhappy when I kept slipping up and being too formal with them afterwards... :)

I think the issue is people you never talked with before! For people I know, you’re right, they prefer du.

That must've been quite some time ago.

With multiple areas with >50% migrants you can count yourself lucky if ppl even speak German fluently enough to hold a conversation.

And the last holdouts that are still mostly natives are usually in the countryside... And the du/Sie rule has always been an urban convention.

Personally, I think your friend just noticed the phrasing and made an issue out of nothing