Historically there has been a pushback on a WG holding an interim meeting
instead of meeting at an IETF main meeting. Yes, cross-WG communication and
all that.
However, looking at my schedule, I really can't see myself justifying what
will be a two week interruption to fly out to Yokohama for a two hour
meeting and more importantly, I don't think many of the folk who I would be
looking to collaborate with at that meeting will either.
Now that IETF main meeting time is becoming an increasingly scarce
commodity, perhaps it is time to re-evaluate the old view that interim
meetings should not be a substitute for having a session at a main meeting
and instead start encouraging that for certain types of work.
Particularly early on in a WG, a two day interim can be a lot more use than
a two hour main meeting event.