Don't think you'll find many schools telling you to use autopilots during training over here in the UK. I was shown how to use it and have used it since but I never touched it in earnest during training.
The general justification is that you are learning to fly the aircraft, not an autopilot and should it fail, you will need to take over regardless of flight conditions. Small twin APs have no redundancy (except you!) and tend to be pretty simple. They aren't clever enough to cope with too much turbulence and are probably not that reliable in general - I've flown quite a few AP-equipped aircraft with an AP circuit breaker locked off because the AP doesn't work...
I reckon that flying should be learnt first. If you are not really familiar with the aircraft's handling, you will be at a disadvantage when using the AP. It's not set-and-forget - you need to monitor what it's doing and be ready to knock it out if you don't like its input. Single pilot IFR ops are high workload but not unmanageable and the AP can't cover you for the whole flight anyway, so I don't really accept that justification I'm afraid.
Finally, isn't half the fun of single pilot being allowed to do lots of hand flying? Plenty of time to play with George when you get to the big boys...