Right. And even though someone "might not need that power" or something, it's future-proofing again. Think about how long people were/are using their iPad 2 and translate that to an iMac with 6 cores. These things (especially with SSD) will live a long life
And if the 2018 MacBook Pro is any indication, this could also be the biggest performance leap in the iMac since around 2011. Definitely worthy of a 20 year anniversary release!