Are all three pieces laser cut? If so how do the screws hold them together if there are no threads?
I don't use Laser for these cases.
Laser has difficulty in precise manufacturing.
So they are all CNC milled and as you guess they have thread on the bottom plate.
And there is no way to make MX switches fit to 2T AL plate if not CNC milled.
(Laser cannot make different depth but just making holes...)