If a dev told me it was ‘easier’ to develop web on a Mac, I’d know they were inexperienced or just wanted a company paid Mac.
First of all, if they’re a good developer and they want a Mac. Fuck me just give them one yeah? Chances are they’ll look for a job somewhere else if you refuse, and you’ll spend how many hours interviewing / inducting / training potential candidates, rejecting most of them, and for what, to save a few hundred bucks?
Anyway you’re dead wrong about web development being the same on all three platforms. Docker in particular is a completely unique beast on all three, and Docker is currently the easiest way to do web development on all three platforms. It runs native on Linux, in WSL on Windows, and in a VM on a Mac.
Of the three, the Mac is by far the worst way to run Docker. But the Mac has other advantages, just to name one they have a proper debug environment for the iPhone version of Safari. I could name others, but the only one I’ll mention is the Apple Silicon chipsets are really nice.