The preflower developed before that and it too looks like a pollen sac.
nanners can be ignored, for the most part. Pollen sacs are a serious concern. Pluck them and hope they don't come back. If the plants keeps growing more of them, better to just trash it before it wrecks other plants... you will miss a pollen sac eventually, and it will cause 100s if not 1000s of seed. a handful of seeds won't ruin quality, but "enough" pollination wrecks potency. Once heavily pollinated it's just focusing on the seeds.
I remove plants that grow pollen sacs. Each to their own if you want to risk other plants or not. As long as the pods are closed, you are relatively safe from pollen, if you mull it over in the meantime.
nanners - had two plants nanner out on me - some sort of stress as it was all over the lower half of both plants. Not just a handful, but nanners at every lower growth node, just about. I removed the first plant just to be safe. The second was a bit delayed growing them and i was pissed and kept it out of spite. I pruned off what i could, but definitely some nanners persisted. -- I've found 1 seed so far, and based on the development of the other plants, it's highly unlikely i'll find many more. Nanners are worth plucking or even just ignoring. They are missing necessary anatomy to mass-produce pollen and often what little pollen it does release is inviable.