Some comments I’ve made here on the topic:

https://news.ycombinator.com/item?id=21244656

https://news.ycombinator.com/item?id=20956850

The currently-implemented viewport units are just fundamentally bad. And I’ve only been talking about the badness of vw; vh has further troubles of its own on mobile.

What was Firefox's former behavior for viewport unit handling that other browsers didn't want to go with?

https://github.com/w3c/csswg-drafts/issues/1766 is the main link that explains it, https://bugzilla.mozilla.org/show_bug.cgi?id=1468684 is also useful.

It's not that bad... it's just scrollbars and mobile where things get messy.

Worse than that. Different browsers and different platforms handle scroll bars differently. Some are hidden until hovered and some have width and some don't some only have width when hovered. It's really awful if you're trying to do something with several scrolling columns

Why would you do something with several scrolling columns? Scrolling elements inside scrolling elements (such as a page) are an anti-pattern