(I know I'm doing my part carrying this off-topic - sorry)

It probably doesn't become apparent until you get to a large scale battle that compatibility does not equate parity - its merely the first requirement. Parity/consistency means that the non-Tamiya system that you use has to perform at the existing standard in every measurable parameter. Off the top of my head:

Similar optical performance (firing and receiving hits - this includes IR receiver sensitivity, IR emitter output strength)
Programming - ability to set up the tank for weight classes, with the corresponding hit points, reload time, and damage simulation

I think its a decent compromise to sell 3rd party boards that have the ability to be configured for Tamiya gameplay by the end-user, though it can be quite a frustrating process if you are new to the game.