Aaah! I just grasped that.
When I said that en/decryption done by the drive, itself, rather than by OS X (should have said "by the OS") seems to be limited to Windows users I meant that when I've seen the option (on HDDs only, I believe) it has been bundled software that disappeared when the drive was formatted for Mac. Sorry for not being explicit.
I believe what you are seeing in Windows is
not hardware encryption rather the same thing found in OS X under the sobriquet FileVault.