The mismatch is the "only one" vs "using one" switch comment. That would be an insane circuit with time and material costs to match to meet residential code with 18 devices and a handful of switches covering every door, stairs, etc. I did a complete rewire of a large house a few years back and went with Lutron for this exact purpose. Yes, every light has (at least) one physical switch in the primary location. But it's $30 and 15 minutes to add each of the (wireless) secondary switches at every location. It is a huge benefit to time/materials/flexibility/future proofing.

It’s a hell of a lot easier to just… not do that, though. I also have a Lutron system and it was amazing to be able to wall mount a wireless remote to add an extra power switch rather than rewire the entire room.