That would be weird. Thunderbolt 3 supports 2x 4K60, so this should as well.

I keep seeing comments about lack of MST support but they're ignoring that you can currently already like you say drive dual 4k60. I'm doing it right now.

You probably has monitors with native thunderbolt input? They are not that many such monitor exists. Without MST you are out of luck to do thing with Display Port (via DP, mDP or USB-C), and this is what majority of monitors on market has.

No, they're both DP. Thunderbolt 3 can do dual 4k60 over a single cable (including also providing power, ethernet, audio, etc) https://www.caldigit.com/ts3-plus/

OSX doesn’t support MST.

Perhaps not (I've never tried daisy chaining) but a MacBook Pro can drive two 4K@60Hz monitors over a single Thunderbolt 3 dock cable (I'm doing it right now).

You don't need MST to be able to connect to 2 monitors