Flightpower is one of the few brands that manage to use pretty poor connectors on their packs (and thats after improving them a while back from very poor connectors).
The trouble is, there isn't any point in him supporting the use of a V Balancer on Revo packs - the V Balancer is not good enough at it's job and he would get support calls asking why the revo pack he supplied is no good anymore, when it's nothing to do with the pack.
The shunt in the V balancer is not up to the job of diverting current effectively, thus it can result in an overcharged state for one or more cells.
It's a complex thing, LiPo stuff, and I do not profess to know all there is to know about it (far from it!), but I get by
, o.a. Aurora.