Personally, I think it does. (or rather it depends on your sound preferences)
I have a pair of Demo UM Aero on hand,
(and keep in mind, these are loaner universal demos, not full customs)
the FR is the same as SM3x6, except without the mids dip (500hz-1.5k is straight) and there's lower end shelf boost of about 1-3db to all the frequencies below 500hz.
I find Aero to have less mids than I'd like (and consequently the highs are brighter than I like), but EQing down the lower end and the 300hz-1k range to mimic SM3x6, makes it very unpalatable for me. (it goes from 'I wish these had more lower mids, but I see why people might appreciate the sound signature' to, 'mmm I think I better take them off singe it's really not what I like/want')
If you're a mids person, I wouldn't recommend it, unless->
I wish UM offered a choice for what the end sound sig of the re-shells was (provided it's possible with the drivers you give them in your IEM and the drivers/cross-overs they have)
(e.g. 'dip in the mids, bumped bass and highs', 'straight mids and bass, bumped highs'... have a look at the last few pages and you get a feeling for the general flavors. E.g. SM3x6W for warm bass and mids dip, SM3x6M - for prominent mids, SM3x6SH - straight up to highs )
That way they'd get a tighter match between what a customer will get from the driver upgrade and the kind of sound they prefer. (perhaps $$$ driver upgrades for custom moulded IEMs are not the best place for trying new sound sigs )
(p.s. plz don't kill me, Matt )
and if they "did" change the acoustics, and you decided you didn't like them.... then what?