Lab caches have only just been added into PGC. There is still a lot of work behind the scenes to fully integrate them. This is happening, be patient!
There is a lot of other behind the scenes work that happens that we don't see - things like server maintenance, code optimisations, and every now and then Ganja1447 wants to go out geocaching. He also needs to sleep sometime. Integrating lab caches is on the list, it just that Ganja cannot devote as much time on it as you and I might like.