It's pretty unlikely that they would do it for their customers, especially since they sell faster models, and have negative motivation for losing money by selling customer-adjustable lower-speed models that are otherwise functionally the same as the higher-speed models. Aside from their accountants, they probably also have lawyers that would object to this, as well.
It is much more likely that they originally used controllers programmed by the controller manufacturer (which is almost certainly not Batec) for each different model. So they'd have to keep around a bunch of different models of controller, and ensure they don't get mixed up during build of the various Batec units.
Or they used programmable controllers, that then had to be individually setup for each model, with the risk of bricking the controller if anything goes wrong during the process, every time this is done.
Then they decided to use switches (taht probably simply ground or let float a few signal lines to the controller's MCU, in the same manner as a common 3-speed controller) to make it simple for the Batec factory workers to "instantly" setup each unit, choosing from a list of preset speeds, and to easily convert any unit to any other speed version if the need arose.
At some point the 3-pot design came up, probably to make each of the three speeds completley adjustable, to make it easier to satisfy changes in local laws for wherever they sell these. There is probably a chart that shows what "o'clock" position to put each one at for what speed, and then a simple offground spinup of hte motor to verify it's set right, with any fine adjustments able to be done then. A bit more complicated than the switches, but more versatile, and probably a lot easier and less error prone for the average factory worker to setup than hooking up a programming cable and using probably-glitchy software with poorly-designed menus and whatnot.
Just speculation...but based on evolution I've seen of actual products that I do know some details about.