But doesn't TS block 2 adjacent seats on a non-full flight for a GCH? I raised this a few months ago and a hugely knowledgeable poster on here stated this can sometimes be the case (can't remember the conditions it can occur though)
I'm not sure what you're asking here. OP says that the middle seat wasn't available for selection at any point - my suggestion was that this couldn't be down to TS as that only has any effect 72 hours before the flight. I am assuming that the OP booked before this time, of course.
I don't know about TS blocking two seats. As a window sitter I've only ever had one seat free unless the flight was very empty indeed.