It is a common misconception that h3 is equal area. At any resolution level the cell size varies by a factor of 2, which is (roughly) the same as S2.

See the following visualizations for an illustration:

https://a5geo.org/examples/area

https://a5geo.org/examples/airbnb

Note that I wrote “roughly equal area”. True equal area doesn’t exist. I am on record that for analytical purposes, equal area largely doesn’t matter.