I use it on my Janome . . . . BUT only spray it towards the left, away from the electronics. AND I only do it after I get MOST of the dust bunnies using my brushes. My dealer even gave me a pat on the back for have a clean machine! He is the one that explained how to use the canned air.
If you use it only to 'finish' cleaning, then you should be okay.
IMHO I think dealers say NO is that many would just spray ALL the dust down to the base and electronics . . . that would scare me to death to open up those machines.