Especially as this would be a downgauge to a 332, which only has 19 J seats. The 333 has 29, so if full, that's 10 pax who would be facing a double downgrade. The flight would have to be particularly empty in J if they could accommodate all in J plus upgrade some Y+ to J...

Perhaps those reports were from way back when, when Y+ was first being fitted, as a few rows of J were sacrificed to add Y+?