Ok thank you guys. Maybe I just didn't notice it before & was surprised when I saw it. I thought maybe I was missing something since I thought that all square bases had been purged from the game.
I noticed on GW online shop that models that were recently out of stock but are now in stock (Skaven Arch-Warlock for instance) have BOTH round and square bases listed in the descriptions. Why are they doing this - is it because of Warhammer Old World?
"This set contains one metal Arch-Warlock in six parts and is supplied with 1x 32mm round base and 1x 20mm square base."