it's Apple making their new OS 64 bit only.
This was promised in 2011 and was supposed to have happened with Yosemite but Apple kicked the can another 5 years.

It's now really real with the release scheduled for Sept. 10.
Me too! I don’t want to update from Mojave. It works just fine.

Then don't.
I would just like to use the DAW plugin, and some new real tracks would be handy. Can PG not have a .version for those that are not going to update to Catalina?

Why do you think that a 64 bit only version will not run in Mojave?

64 bit only apps have been real for many years. Some run in Snow Leopard.
BIAB 2021 Audiophile, 18 Core iMac Pro/4TB/128GB Monterey; 2012 MBP Catalina
Digital Performer 11, LogicProX
Finale 27, Dorico 3, Encore 5.0.7, SmartScore Pro 64 Notion 6, Overture 5