See this thread for details.
Left/Right Spits in fictional league
As an executive summary, batters created in a fictional league (or a quickstart fictional) have significantly different ratings vs L and RHP. As one sims forward these splits converge over time. About 8-10 seasons on, you have all batters with the same ratings (4 or less on 100 scale) against L and RHP.
I've checked out several variations of fictional leagues and it appears to be very real. Not able to pin down how far back (in builds) this may go.
IMO this is a very serious bug that makes playing Fictional leagues a waste of time. I hope that Markus can look at this before the third patch is finalized.
Edit TT3888 has been logged