Yeah, the runner at second is not retro by any means. But I'm not really bothered by it. It's just different and it could make for interesting strategy decisions. I was at a minor league game a couple of years ago where the leadoff batter in the top of the 10th squared around to sacrifice, and I was befuddled until I noticed the runner at second base and remembered the rule.
It's not retro, it's just different. Football and hockey have messed with their overtime rules in past years, and there is no problem. If they play ball this year, so many things are going to be different, that it makes sense to try this kind of thing now.
I'll admit I didn't particularly like the idea when it first came up a few years ago, but that was because they weren't really addressing the root cause of the long games, which is all the dead time between pitches, hitters, and innings. I don't mind long games, but it can be frustrating when nothing is going on.