This should not be the case. I understand that motorcycle helmets are not removed at the scene unless absolutely necessary, but this should not be left to the police alone. The paramedics shouldn't be banned from removing helmets themselves anymore just because they were sued once. What if they ran someone over? Would they decide to stop using ambulances, choosing to walk everywhere instead?
The level of treatment you expect to receive from emergency services when you need them the most should be consistent. The paramedics shouldn't be forced to stop removing helmets because that does not address the issue. The helmet still has to come off at some point and if that point is at the crash site a police officer may not be as well trained and practiced in overall first aid so this may increase the risk factor. If the helmet needs to come off there and then, they shouldnt have to wait for a police officer to arrive at the scene if they are the first ones there.
Perhaps this extends further, perhaps paramedics should be allowed to perform a range of procedures and actions which are enshrined in law more strongly without fear of repercussions from their leadership for causing additional injury, so that if the action they take results in further injury, the person will still be compensated, however, the paramedic and organisation they work for will not be punished so badly that they cease treating people in the best way they can, as it isn't fair the police should shoulder that responsibility.