Interesting, and surely a glitch. I reached the dizzy heights of bronze and have just done a BA club class return to the states. Both going out and coming back I was was able to choose seats at 7 days to go, and that included my travelling partner who is only blue in her own right.
We have just booked flights for next year and was told when booking that I would be able to choose our seats with 7 days to go - so it must be working somewhere.
What is perhaps more interesting, is how the seats are released. For the flights in a year's time, there are apparently already no seats available upstairs (747) - I can't believe they are all allocated already. On the recent trip, upstairs appeared to be full right up until the 7-day point when 2 seats became available - so we had them.