Besides that, there isn't actually obvious different between firefox/chrome/edge on macos/windows.
The most problematic one is actually safari(which is on mac only). If you dev on chrome and use on firefox or vise versus. You usually get a "mostly work with minor visual different". But safari… will give you a fail and are't even usable. It is outright the modern age ie.
Doesn't sound sexy, no. Compensate them royaly. And make clear that they are superstars just by having this work environment. Then keep listening to what annoys them with whatever you are building, and let them fix it.
That, however, is bound to happen even if you have Windows workstations. It happened at a job where I was, in fact, running Windows, because the designer ran macOS and was oblivious to this issue. (Of course, I would fix it when spotted. But it still managed to make it out to prod at times.)
Or, leave the default settings in place, but plug in a mouse with a physical scroll wheel.
So it's not even that they're only using one platform, but they're only testing the platform with default settings with the default hardware. And we're not even talking about an obscure setting buried three levels deep, it's right there in the general pane!
sudo defaults write -g AppleShowScrollBars -string Always
I include this as part of my setup script for any new Mac.But I also place the blame on design teams. Most design teams I've worked with also doesn't account for this in anything they create. They usually only design for: 1: the latest macbook pro; and 2: the latest iPhone.