If you use a large prop for reasonable power the speed issue offers protection. If you use a small fast prop you have less energy capture from the prop and it needs a higher wind to reach the same power out.

Added to this most people using Amtecs are starters, often using pvc or other poorly designed props and this further reduces the risk.

With a good well designed prop and no furling in a high wind it is perfectly possible to burn one out if the bearings hold together long enough. How many amps it will take depends on the duty cycle of the loading ( wind conditions) and time. If you run one on a bench rig you will be limited to something like twice its nominal rating to burn it in a short time. With wind you may have a factor of 3 over this so peaks of 20A may be survived for a fair while before final failure.

Only tiny machines will survive without some form of power limiting and even then I don't feel it justified not to furl or provide some protection.

Yes they are very much starter projects or something to supply small requirements, most people seem to expect too much from them. I really don't see why the sudden interest in such silly things, fine if you accept the limitations and want to start somewhere, but there is a lot of information about suggesting that they will do wonderful things.

These things are ok for a tiny set up in a remote cabin or something but for more serious use you need something  much larger unless you are in a very high wind area.

Don't worry about burning it out at 3A or whatever you got.