It's fairly common amongst my colleagues and I in the UK.
I suggest the scenario was something like this:
You were at a level above FL200. The controller had traffic at FL200 which he knew would conflict with you if you were left to descend when ready all the way down to FL120. So by pushing you down to FL190 he solved the conflict against the FL200. However, he probably realised that this would put you below your usual descent profile so, with no further conflicting traffic between FL190 and FL120, he left it up to you when to descend to make FL120 by any restriction point or on your descent profile.
Sound reasonable?
I often do it on GW/SS arrivals from COA which come in descending to FL270. They need to be FL180 at LOGAN, but there is often crossing traffic at FL240, so I will descend the SS/GW 'now' to FL 250 and then FL230 to get underneath. The descent from FL230 to FL180 Level LOGAN will then be 'when ready' (provided there is no further conflicting traffic).