I'm not actually sure that's true, the Miyata Pro / Team didn't get fastback seatstays for a few years afterwards. (the 1986 Pro Miyata iirc)

There's a frequent idea that Univegas were basically rebadged Miyata bikes (ie the Competizione was a Pro Miyata and the Superstrada was a Team Miyata) but there are absolutely differences.

Anyway fastback seatstays are cool so my verdict is that it's even cooler than a Team Miyata.