I don't think that's right - I was upstairs on a 747 a couple of weeks and only 64A had a bassinet
I'm looking at my next 747 upper deck booking in a few weeks and it shows as usual 64A blocked out with the bassinet, and 64K open for selection (and occupied on the return)
I think the agent is getting mixed up and perhaps seeing 64K as blocked/unavailable to you if it's held back for BAEC Gold (Silver also?) for now, and then getting confused with the bassinet?