Exactly. By “clearing the deck” of all APIs (and software using them) that won’t make it to ARM, they can position it as the same OS and apps, just running on a more-efficient chip. And for 90+% of Catalina-compatible apps, a recompile is all that’s needed. (And/or they’ll have an emulator)
In the PC world, 2-1 like the Surface are taking over classical laptops.
Are they? Certainly not in sales.
There was a push to make all laptops have a touchscreen a few years back, but this seems to have fizzled out, and I've seldom seen anyone use them (deliberately anyway).
I actually suspect the move to/inclusion of ARM in the macOS lines of product is part of the motivation behind dumping support for 32-bit apps in Catalina. By preemtively removing support for a large amount of legacy software, which will likely never be recompiled for ARM, they avoid the situation where their new machines appear much less capable than the old ones.