Slumming in economy later and hopefully my flight wont be full, so I moved myself from the exit row to half way back in the cabin to an empty row.
Checked the seatmap again later to see how things were going, and the two seats next to were blanked out.
Not sure if that meant I had seatmates even though over half the seats were free, but I moved myself again, doubled checked a little while ago and the same.

So do AY actually block seats (got my BA Gold number in but will change that once i get my bag checked etc.)?

I know BA allegedly do "theoretical seats".