That's not technically true. You are never using more than one pick at the same time. You do need a tension tool, though, which neither of TDM's picks are and we might thus assume it's just implicitly there.
The only thing that's potentially unrealistic is regularly needing both picks for a single lock. Because while that may be needed in the rare case, it's not a common theme for common locks
Well, and the whole process of picking a lock in multiple stages is also not exactly how that works, but then again, it's a game, not a lockpicking simulator...