I have not had to bleed the new pumps, use to have air lock issues all the time with the older style pumps.

At work i deal with lots of pumps, impeller, mostly steel, also AODD <air operated double diagram pumps that will pull vacuum till liquid is present but prefer liquid> these lose prime from time to time and you have to reprime them. Also I have seen issues with too much head pressure on the back side of the pump cause an air lock where the pump is running but just can't prime.

I think this is what the dealer means when they say it has to be bled. The real problem is there is no head pressure on the back of the pump, but if the pump is sucking in air through a hole or a large kink in the line this can cause the impellers to run dry or at least hot. Both of these instances can damage the impellers.