'and even then every design professional would laugh'
At one point anyway it became an 'exclusivity' thing for many, and in the 'arts' sector many are easy prey of the 'bling' factor, especially the beginners and the wannabes. Those 'laughing' are usually these.
Accomplished professional will use whatever give them the results they look for, although evidently confidence in tools used for years matter. While those writing books can't address only 10% of the PC market, so avoid to laugh, at least in public. Anyway, once you launched Photoshop, Illustrator or InDesign, today the underlying OS matters little, and become mostly a matter of what you used to.
It is true that the whole workflow pipeline was mostly built around Mac hardware and software, but today if your PDF/PSD/TIFF/etc. come from macOS or Windows matters very little, as Adobe ensures full compatibility. Moreover nowadays very few deliver images on physical supports that could be incompatible, a big issue years ago. All the services I know let you FTP your data (old choice, but it does work) and even on portable disks some version of FAT became the defacto standard.
There are still high-end software only available for Mac, i.e. some specific print processors, which still give Mac a little edge, though.
Apple can still rely on its status to sell its MacPro line without much innovation and few choices of hardware, i.e. GPUs. How long Apple can rest on laurels is yet too see.
But Windows too in the past few years looks to have returned to its older habits, a lot of emphasis on the generic user, far less on specialized ones.