Does the lower mass of Uranus suggest it swapped position with Neptune? As Uranus is less massive than Neptune, would this be evidence that it was formed further away from the sun than Neptune, and later it swaps orbit with Neptune to move closer to sun?
The Nice model of solar system evolution proposes that both Uranus and Neptune migrated outward from their original orbits due to numerous encounters with planetesimals,
stimulated by a temporary 2:1 resonance between Jupiter and Saturn.
Simulations going back billions of years can put either Uranus or Neptune initially closer to the Sun.
Desch 2007, assuming that the Nice model is correct, argues for a particular density profile of the protoplanetary disk and notes that a closer proto-Neptune fits that profile better.
Some solar system scientists have problems with the Desch model, but Uranus's smaller mass is consistent with it.