it isn't a bandaid, it is how it works.
There are multiple paths to ground. As long as your coolant has enough iron from the block to be conductive this is going to happen.

More grounds on the block will help.
grounds on the rad, (since it is bolted to the body) probably don't make so much of a difference, if anything, I would isolate it so it doesn't give a path to ground. Thus preventing current from flowing in that direction.

Zinc anodes have been around a very long time.
Aluminum radiators have not been common for our old cars but are common for new cars and most have something like that.