As I understand it, those “postcode centroids” come from old and incomplete data. Even if they were accurate and up to date, they’d be entirely artificial constructs, and so wouldn’t belong in OSM. I think they should be removed (after appropriate discussion and concensus).
There’s also no official concept of postcode boundaries in the UK. Postcodes exist only as assignments to addresses. So again, I don’t think such artificial post code boundaries belong in OSM. (In any case, you’d actually have trouble trying to create boundaries, due to large-user postcodes, non-geographic postcodes, various other anomalies.)