Mac client update to 64-bit — minimum OS Mojave??

I'm a new player, and I just read that the Mac client is transitioning to 64-bit, and that the minimum system OS version for the 64-bit client is Mojave.

I am running High Sierra on my Mac, and I will not be able to update to Mojave any time soon—it breaks a number of apps I use.

Is this transition to 64-bit a hard one—that is, will Final Fantasy XIV immediately cease to work on macos <Mojave? If so, I'm going to have to stop playing. I sure hope you consider supporing High Sierra for the 64-bit client. It isn't that old.