Bleeeh! It worries me a bit that game developers could fall into putting technical pedantry before consumer experience. If your customer sees a jerky update then your update is jerky - how very clever you might be being in the background really doesn't matter one iota. *I know* you're addressing developers here, but I still think it's genuinely important to bear this in mind: Untrained eyes are the eyes you ultimately have to please.
All commercial games do this, what exactly is the problem? bigger gaps between movement is the nature of the beast when pcs slow down.
In the old days the actual time would slow down instead so you were running through glue. You prefer that??