Yes it is a game to catch young and not so young players.
I measured 8 degree difference on an old Lucas
K2F mag due to bad armature alignment. I kept trying to fix it by grinding the cam ring and ruined a second set of pistons before I finally realised. I was being a bit stupid really and should have figured it out earlier if I had not been diverted by other issues.
On my race bike I set ignition to within 0.5 degree both sides and have experimented with the dyno to get the best setting for petrol and methanol.
Many magneto servicing places address the electrical issues but not the mechanical issues