Yep, this is a bug. Because OF positions are broken up by our data provider, the system adds up all the different OF positions a player has played to get to their OF game total. So, if someone plays 2 games in LF and 3 in CF, the system shouldn't treat those as separate positions and not give OF eligibility.
The bug was that this did not qualify OF totals per season. So it added 2 LF games from last season to the 3 LF games from this season and made 5 OF games. That's why the bug doesn't affect non-OF positions.
I'm fixing the bug but will give Schwarber manual OF eligibility for the next day, after which he should qualify due to 5 OF starts.