That is for iPad and I phone only.Not for I Mac’s.
Actually, no, it's not.
It may be that your OS doesn't support the download (see post above). In other words, if the hardware won't support it, then you'll get an error message when attempting to install it.
If you have an earlier version (such as El Capitan), the download may not install. And if you have an older system, your hardware may not support Catalina.
I have Catalina and was able to install it using the download link. For the list of Macs that support Catalina, see here:
By the way, you do understand that both the Windows and Mac desktop versions are graphically similar (if not virtually identical) to the mobile-platform version, yes?