Mostly, in my mind, it's that Lando has the lower pilot skill
Lando has a PS of 7, that's still pretty high, higher then any generic out there. I don't see what his PS has to do with Jan's ability. Unless your trying to use Lando to give Jan another action. But Jan doesn't need extra actions typically, she's there to hand out dice to other ships. Other then that, there's no real interaction between the two that PS has any effect on.
Lando's ability is more of a support thing, then Han's reroll which is clearly offensive. But Han's ability isn't really that good, because it's so seldom used IME.
The problem is that if you're only running 3 ships, and two of them cannot benefit from Lando's ability, then killing the third effectively removes that ability entirely.
Also, Jan, having a higher PS than Lando, means that she'll ALWAYS be stressed when he's rolling out his free action. 'S a no-go, mate.