A lot of those have other switches than Cherry MX.. Chery ML and MY are quite common, for instance. Also, most of the newer Cherry MX boards (G80-3000 series for instance) are fairly cheaply made in terms of being just a PCB with switches in a plastic case. No plate, poor PCB support, thin keycaps and not very solid. Some come with PBT keycaps, but they're thin, light and the legends are lasered, not dyesub. If you add a backplate for support they can be acceptable to use, though. But if you also want to put better keycaps on, etc, it's better to have a more solid board as a starting point.
I think some of the POS boards have plates, though, and probably feel better to use than the modern G80-3000 series.
I recently bought 2 new Cherry G80-3000 boards for the switches alone (Clears) since they cost less than buying the same number of switches separately would. As a bonus I got some thin PBT caps and PCB mount stabilisers
