Actually, yes, the above-posted interpretational table is still correct (and the data in your reply post further confirmed it).
No, on the 178 Flight you're showing 1K and 33 A/E/F/K all as "X", however they are
different according to BA. 1K is Premium Only Available, while the row 33 Seats are Blocked, but available. As per the GDS XML I posted for the flight, 1K has the Characteristic of "O" (which means Premium Only) but the row 33 seats don't, they just have the "1" Characteristic (which means Blocked).
They are different for a reason, as Blocked can mean "blocked for airport assignment", it could mean "Crew rest seat", etc etc, a blocked reason could easily be regardless of status. So you're showing two different things as the same, which is wrong, and very misleading also as the "P" symbol usually indicates Available - Premium Only on websites, not Unavailable - Premium Only.