Right, despite my OP asking to be able to run iPadOS and macOS apps on one device depending on usage, what I must have actually wanted is a device that can do neither.
I mean, a Surface Pro starts at $800 (or closer to $1k for a proper setup) while an iPad $350. The vast majority of iPad sales likely come from the lower end. There is no way to compare their sales number.
The fact that it isn’t mentioned is probably a testament to how poorly it sells but Microsoft does have the Surface Go for $499 to compete with the iPad Air.