You do also get double the storage, double the RAM and a 24 megapixel camera upgrade.
Traditionally, the amount of RAM in your device is the limiting factor that controls how many years of updates you get.
So far, 8 years for the OG iPhone SE is the standing record for years of updates.
And the OG SE was significantly cheaper, even after adjusting for inflation. But it only received 6.5 years of regular iOS updates. It was released mid-cycle with iOS 9, and iOS 15 is the last supported version. You may be counting the later security updates, but that doesn’t help with app compatibility.