Hi Matt, I believe Giant dealers don't ever crack the motors open for servicing, despite
some suggestions that the motors would benefit from regreasing ever few thousand kays. Same for most of the other brands. I assume the motor manufacturers have run their sums on cost of motor failure within warranty versus cost of training and 'things going wrong' during servicing and landed on the existing model. Sucks if you plan on hanging on to your motor well out of warranty and/or do a lot of kays, though to be honest I'd venture most consumers don't ride far enough, hard enough or in the sort of weather to create issues, well maybe just the eMTBing crew. 5300km here on my Syncdrive Sport with no motor issues.
If you do have problems outside of warranty you could give this mob a go:
https://www.facebook.com/ebikemotoraustralia. They service and overhaul Yamaha motors.