It doesn't have to leak, brand new seals will sing. It's a sonic resonance set up at the lip of the seal on the balancer. It has nothing to do with being old, dried out or burnt up which I said nothing about, there's more of that reading comprehension thing....Scoring the hub breaks the surface tension and disrupts the vibration, which is what that is you are hearing, a very high speed vibration similar to disc brake squeal.
Oh and BTW, I'm not retired, I'm still bangin out 60+ hours every week at 53 years old. My 20 and 25 year old sons are both techs at the same dealer I'm working at and they can't beat the old man. No amount of enthusiasm and energy can beat experience and ability. And tools, I have more tools than them. lol