[ehsankia]

Historically, they have. Older pixels all had 2 year feature 3 year security, but ended up getting 3 year feature+security.

Although, after 1-2 year, the features get a bit thinner because a lot of the newer features rely on new hardware that the older phones don't fully have. Sometimes they try to make it work, like how Astrophotography was available on older pixels but didn't work quite as well as on Pixel 4. But in general, they probably put the "at least" because it's hard to guarantee that a feature in 5 years will be backportable to Pixel 6.