Bold by me.
This might be the key. I started with historical numbers and tried to come up with numbers that look very much like they could be historical numbers themselves and then I just put as many of them as possible into OOTP. EDIT: I don't actually pay that much attention to historical totals themselves. I look at various historical ratios, tweak them, and then convert those tweaked ratios back into my own ideal totals.
So, for example, it's not a problem for me that OOTP might not have certain stats like RBOE or RBOI. Yeah, I'd very much like it if OOTP had those stats and if certain players were better at them than others (Ichiro and Ellsbury), but for league total purposes I just come up with plausible numbers (and for anyone who doesn't know, you can
download the lahman database of historical baseball stats from SABR (particularly teams.csv) EDIT: or FanGraphs which has some data lahman doesn't (
Batting,
Pitching,
Fielding)) and then I just input into OOTP what I can. So even though I'm not inputting stats like RBOE, RBOI, and whatever else, I'm still factoring them into my totals and ratios, they're just not inputted into OOTP is all. And so if someone doesn't factor in these other stats into their PAs, the game might not have the "fudge factor" it needs to make everything fit. If OOTP had all the stats as inputtable, it probably wouldn't be a problem, we could just input them all. But since we can't, if we don't leave the engine enough room to do everything it needs to do (IINM, the outcomes are there, the stats just aren't), then it likely needs to take away from something (in this case, iBB) to give something to these other things. And considering iBB was the most recent addition to the era_stats file, I'm not surprised if it's just taking from it instead of something else.
Or maybe I'm totally wrong. It's just a theory.