As a versatile defender who can guard 3 and 4 (occasionally undersized 5s) and be good to great depending on the matchup, yes, I think T-Rob can be that. And I think this is Smart's point - the versatility.
As a lock down big man defender a la PJ Brown, Hornace Grant, etc - nope, don't see it (but I'll be happy to be wrong).
I always thought T-Rob's size, physical tools, and relentlessness are similar to Rodman's; but Rodman, as great as he was, still occasionally had problems defending those bigger fours (particularly when the refs were calling it tight).