Is the difference with our flight ( all UD seats available to me as a Blue) due to the fact it is the 52-CW version? Is that what is called "low J"?

I am trying to recall what the seating availability on the UD looked like for our last BA flight, which was on the 70-CW seat 747. We chose 63J and K (usually do) but I vaguely remember seeing the 62 row not available.

Seems like many here favor row 64, but isn't one there at risk of being bumped out by passengers with an infant?