when i was considering buying one of jimmys basses this was an issue i talked about with him regarding the lm's. i a/b'd basses with my 78 jazz and told him i was looking for a 70's style 5 that had the type of high end my fender did. i wanted pickups that had that sound to begin with rather than trying to dial it in with the pre because imo, adding the highs in with the pre starts sounding electronic or processed.
+1 I can honestly say that I've yet to touch the treble boost control on either my LG or LM in the years I've owned them. Both those basses sound reasonably 'period legit' to my ear (close enough in a mix anyway) in passive mode, and as you've heard in my clips, the only difference in active mode is the classic buffering effect you get with any active circuit (a bit more deep low end and a bit more sparkle way up high).
Seems like Jimmy revoiced the LM's quite a bit from the New York shop days based on Tom and Peter's comments. I guess that isn't good nor bad, but I like that very pronounced upper mid grind that, to me, defines the 70's sound. There still seems to be some confusion by some thinking that LG's somehow don't have treble extension. If anything, they can sound more 'sparkly' up top, since they don't have that strong upper mid grind that masks the top end sizzle a bit. However, dialing in an active treble control ain't gonna do it for most. Like you say, artificial and 'electronic' sounding. Again, the 70's thing to my ear is all about upper mid and lower treble grind, not pure upper treble sizzle.
As I've commented a zillion times before, the top end of my LG, if anything, has more pure upper treble sparkle than my LM... it's that brightness and grind in the LM's upper mid/lower treble that just kills in a more aggressive pop/funk setting.
That being said, I've played so many 70's J's, and they all sound quite different. I've played ones that sounded close to Marcus Miller's active tone in stock 'off the shelf' passive configuration, and I've played others that were quite dark, and had more mid punch and less grind.
Wood and its interaction with electronics is a funny thing and is quite hard to predict given spec only info.
That being said, Jimmy obviously changed his approach and spec and voicing on the LM's since mine was made in New York. I guess only the individual player can decide if that was a move in the positive direction.