There was a series of tires with a large center groove whose purpose was to channel water through the center of the tread where the water would pile up in front of the tire. The pattern was based on a twin tire concept that had some remarkable performance. Goodyear produced one (and you could say started it, but that is debateable) with one called Hydro (or somethuing like that). Goodyear was not the only one who had this, but they were the most prominent.
So I don't think the absence of a center rib is worth worrying about.