Yeah, these are not POMOs. These are operations known as "passes" (could be either a "coupon pass" or a "TIPS pass"). They were done occasionally by the NY Fed to routinely adjust the composition of the SOMA portfolio and are very different to the modern-day POMOs that are done within the context of the LSAP (Large-scale Asset purchase Program). Specifically, the passes have always been quite small and infrequent, due to their somewhat cosmetic nature.