What's old is new again.
Old timers remember that this was the old way of doing things, until at some point they changed to do full-page zooms, to the joy of developers.
Now they're adding support for this again, but `:root{font-size: 16px}` breaks it, so you're guaranteed to see that in CSS resets everywhere because there's nothing that managers hate more than inconsistencies
"QA user X mentioned that the text overflows when text zoom is at 300%. Fix it."
Yes, functionality trumps design if something has to give -- but what is the text overflowing into? Often it is overflowing into other text, and so now neither is readable. Or it is pushing other content unreachably outside the viewport. In this case, it's a lose-lose situation, in that both functionality and design have suffered.
For example, NYT with 200% text-only scaling: https://i.imgur.com/zp7pDW3.png
The problem there is trying to fit all the content on a single line. Obviously that's an immovable-object-vs-unstoppable-force scenario. Instead, let the layout elements flow downward.
> "QA user X mentioned that the text overflows when text zoom is at 300%. Fix it."
We've adopted a stance that functionality trumps design at larger text scaling. Second, overflowing is preferable to truncating (also as per the WCAG, which says you shouldn't truncate / no information should be lost on larger text scales)