The scores speak for themselves, especially the Geekbench scores which are now where we would expect them to be.
Whatever throttling that was going on in iOS 14.5.1 is gone in iOS 14.6.
It's unclear what the issue was, but in the release notes for iOS 14.6, Apple did mention that there was a fix for an issue that may cause an iPhone to "experience reduced performance during startup." Whether this was the same issue or a different thing altogether, I don't know.
Either way, the problem seems to be fixed, so if you were affected, it's time to update.
And if this isn't reason enough to get you to drop whatever you're doing and carry out an update, then the more than 30 security fixes contained in iOS 14.6 should be.