I don't know what the stats are either, but I agree. Not only does it seem like they cover more often than not, it seems like they win outright more than 50% of the time. Usually, if I like a small dog of less than a fg, I just play them on the ML :shrug:
I once heard that 2.5 & 6.5 point spreads always favor the underdog. I tracked it for roughly 15 weeks in the NFL and it didn't play out so well. maybe 50/50.