I don't think it's cost reasons these are being omitted. The customer refunds would easily exceed the savings. It's most likely designers just swapping a micro usb port with a usb c one in an old design while making no other changes and seeing it works with the A to C cable they have.
I share your theory about micro usb, yeah. I know it’s not cost savings, it’s just lazy/ignorant. If they’re changing the footprint on the board for a type-c port, they can add some smd resistors.