The supported lens box has some very disconcerting information. I'm wondering about 3rd party lenses that should work but will be in contrast-detect just because they aren't "supported". Also, what's the point of having this function work at f/11 if it doesn't work with teleconverters? Who has a "supported" bare f/11 lens?
As pointed out, each lens has to be calibrated. based on the report, it seems they did an algorithm that can cover all lenses. However, there is absolutely nothing against have specific look-up tables for lenses that don't fit the normal algorithm. So, in theory there is nothing wrong with Canon providing firmware updates to include additional lenses. This could also include a separate set of algorithms for say the current 103 lenses attached to the 1.4x teleconverter. After all, it's just a matter of testing all lenses, teleconverter combinations, and develop the correct algorithms. Then load it into the camera body, provided the memory is large enough to hold all info.
As to third party lenses. In the case of sigma, they work already by pretending to be Canon lenses. At least in Sigma's case with their new lenses and the dock for updates, they might be able to make it work. I.e. first, they have to choose a lens in the the 103 line-up, then they have to check that the algorithm works. If not select another lens. Amongst the 103, hopefully they find one that with some firmware update works.