We should be able to desynth the Moonward gear in 6.2. That's pretty standard (the most recent tomestone/raid gear released can't be desynthed or traded for GC Seals until new tomestone/raid gear is released).

I agree it's an annoyance for now unless someone has a lot of open retainer space to be storing those items for another 4 months. I understand that SE is trying to make it easier for players late to the Endwalker MSQ more options for getting some level appropriate gear faster but I suspect most of those players aren't going to have their retainers at a high enough level to get those items from quick ventures.