Because vsync is pretty bad on EOSM.... but the other suggestions do make sense... its really bad using MZ or 10x zoom with the half shutter method (I hate it).
I also guess it's very hard to get the magic room working perfectly but I believe you can figure it out some day. I don't know if it's possible to add the trigger delay option but currently I think it could be the only work around.
BTW, even though I also hate to use the10x room function as a work around, I can actually accept to trigger the magic zoom box with half shutter press if it's not set to be always on. But I just want it only appear after the shutter half pressed and auto disappear after release the button. Just as I said before, it could help us almost use the focus peaking and then the magic zoom together. Currently these two functions can only work alone.