Amusingly, its indeed not really what's happening, since as the GIbiz article states, they are aiming for a more frictionless experience on the Steam side, connecting accounts, crossplay etc. Sounds like the experience will get more "thin" as they work through it. Regardless, Steam seems to have been pretty supportive of all manner of other stores and integration methods, so long as Steam purchases can be fulfilled and managed directly by Steam - ie depots, dlc, marketplace etc
Fallen Order being a late addition, even doesn't have achievements "at launch" but will get it later, likely when they integrate across the two