I assume that you can reformat the Windows version on the Mac without any problems, using Mac OS Extended Journaled Encrypted, APFS or whatever. The Mac version is simply pre-formatted so that the common Mac user is not confronted with difficult questions about the file system.

Dear Digitec,
they write that you can reformat it, ( Hard Drive Utility ?), but I always prefer to buy WD My Passport for Mac directly. That's all I can say about it.