Max,
AS BOAC said, here in lies the dilema. I've just had a good look at our rules, and the only specified weather requirements are for Destination Alternates and ETOPS Suitable airports. It is absolutley laid down that there are no weather minima for Adequate airports (alos known as en-rout alternates) and as such, the assumtion is there are none for the en-route fuel alternate.
The way you interpret it, however, does seem to make sense from a EU-Ops perspective, which we are supposed to be compliant with.
I'll do some more reading and maybe drop it in the CFIs lap...