If habitability actually made sense, it would work very differently from how it does. You'd have essentially "bands" of different climactic ranges on each planet, with the equatorial regions being hotter and the poles colder... but the poles on some planets would be so cold that basically nothing could live there, and on other planets they'd be the only place almost anything could live. This would affect the usable space for any given species on the planet. Similarly, oceanic-adapted life and, say, jungle-adapted life should differ by a heck of a lot more than 20% in how ideal a given planet is for them, because there's a lot more than goes into habitability than temperature. Gravity is also weird. Both "Low Gravity" and "High Gravity" modifiers cause reduced habitability for everybody, even though "low" and "high" are relative terms and some species will absolutely be adapted for lower or higher gravity than humans. Also, although planet size does influence the weight for those modifiers to appear, it's nowhere near strong enough; the composition of rocky planets doesn't vary that much (at least based on the ones we've studied so far), and even a slight increase in volume means more pressure and therefore probably higher density, so anything significantly large or smaller than Earth is almost guaranteed to be meaningfully higher or lower gravity.
