In general we want to be shoving tighter with a limper in the pot. You can think of it like another big blind to act behind you, but one who’s already indicated an interest in playing their hand. Limping off 9bb, UTG may be calling shoves extremely often.

According to ICMizer

If UTG limps 25% and calls 44,A4s,A7,K9s,KT,QJs while BTN isolates 44% and calls 22,A2,K5s,K9,Q9s,QT,JTs: 

We can shove 30% of hands against those ranges and J9s is doing pretty well, winning 0.34bb.

If UTG limps 13% and calls 77,ATs,AJ,KTs,KQ while BTN isolates 32% and calls 44,A2s,A7,K9s,KT,QTs:

We can shove 17% of hands and J9s is a wreck, losing 0.19bb. Against these ranges only 22,A2s,AT,KTs,KQ win more than 0.15bb by shoving.

The big difference is not that they call with stronger ranges, but that they fold much less. It’s relatively hard to know what these players are limping and min-raising with. Readless, I think J9s is spewy vs. a limp and iso-raise, but shove all day vs most BTN or CO openers.