It seems that on the Canon 5D MK III, the SD card slot is limited to a maximum 133x write speed regardless of the rated card speed. However, the CF card slot is designed with the higher write speed rating. Having said that, apparently if you are writing to both cards, the camera will default to the slowest slot (the SD card). So, many choose not to put an SD card in the slot at all. Apparently this is a problem only if writing to the SD card or the SD and CF card simultaneously.
My question is this. Will the camera still default to the SD slot (133x write speed) if Magic Lantern is loaded onto the SD card, even when only writing to the CF card? In other words, even when not writing to the SD card containing ML, would it trigger the same response?