[Hoiles]

Did some further sleuthing and made my way onto the thread. It's pretty evident the NeL pitchers get a huge boost to their movement and control ratings for some reason.

Looking at the single-season 1927 import at defaults, (single season to avoid effects of other seasons and recalcs)

Lefty Grove:
Imported resulting stats (in a modern day MLB environment):
227IP, 6 HR, 64 BB, 157 SO., 3.03 FIP
Real-life (pretty reliable)
262IP, 6 HR, 79 BB, 174 SO, 3.04 FIP

Heliodoro Diaz:
Imported resulting stats (in a modern day MLB environment):
231IP, 0 HR, 46 BB, 175 SO., 2.35 FIP
"Real-life" (according to OOTP database):
172IP, 6 HR, 56 BB, 112 SO, 3.36 FIP

Grove's stats are very close to his real-life ones. Diaz actually had a solid year IRL, but gets a huge boost in ratings based on the assumption that he wouldn't allow a home run in a full season. In fact, 22 out of the 64 NeL starters had a 80 movement rating, whereas 1 of the 193 MLB starters had a 75 movement rating (none 80). The NeL starters' control ratings were also noticeably higher, though to a lesser extent. The NeL hitters don't get a similar obvious boost.

Looking at the league totals in the Stats and AI section, the MLB and NeL had pretty comparable league stats (in fact, MLB had slightly more offense, so Grove should have gotten a bit more of a boost). So it doesn't seem to be a normalization vs league average type of thing.

I suspect we can get a better MLB/NeL balance by fiddling with the adjust/weaken settings, though that might affect the sim quality of the individual leagues themselves.