Even in St. Louis in '82, Drysdale was saying that Wilander already was volleying better than Borg. It's funny how tennis writers and commentators said, year after year, right up to '88, that Wilander had recently decided to add a volley to his game. In '82 his volley already looked like it did in later years, at least technically.
Of course his net game did mature over the years, because it's one thing to know how to volley, another to come in consistently over the course of a match against someone like Lendl. That's what Mats got better at over the years. His net approaches, roughly speaking, were one reason he beat Lendl at the '83 AO; a key factor in his win over Lendl at RG in '85; and practically the entire cause of his victory over Lendl at Flushing in '88.
Borg never came in at RG the way Wilander did in that '85 final, and unfortunately he never did so at Flushing against Mac. On the other hand, Borg successfully SV'd, often on 2nd serve, at Wimbledon over a six-year period, something which Wilander never pulled off successfully despite attacking the net pretty well on Australian grass.
On this board when we got a look at Borg's win over Mac in the autumn of '82, at AKAI, we speculated that Borg may actually have observed Wilander's success against McEnroe and taken a page from it. Pure speculation but possible.
One point from that event: http://www.youtube.com/watch?v=BXitxEkVz3Y