Honest centralization is still centralization. You may be assuming that everyone participating in a mining pool will get an independent vote. From my understanding, this is usually not the case. If a small number of mining pools control more than 50℅ of the capacity then just a few people can decide these types of matters, honestly or dishonestly. That's centralization.

It's not total centralization, but it's a far cry from the level of decentralization that would be possible if mining pools did not exist.