Notably modern browsers can simulate phones, tablets, TVs, really all kinds of screens. I personally use that mode a lot to test the mobile variant, but nearly all bugs are purely CSS-related (at least in my experience) when it comes to a mobile-desktop discrepancy. Either way, for food delivery and stuff like that I'd really expect the devs to develop primarily for mobile, so that's surprising to hear.
Yeah I refuse to debug other people's sites lol so I don't know what's going on precisely but I've noticed this a few times.
We build things as mobile first in my shop but it's really hard to test everything on a real device on every build. I suspect these kinds of bugs are usually a "this small change should work the same everywhere" but doesn't for various reasons.
Oh yeah, that stuff is a pain and automated tests can only go so far. Also I know for me personally I do tend to neglect mobile a little just because I much prefer designing and developing for larger screens, and I doubt I'm the only one, so on mobile more will slip through the cracks when it comes to these tiny changes.
