It's confusing to me. What's the actual standard? Games started?
The 35 start, 200 inning rule is pretty reliable. Exceptions are made if a pitcher had a workload for a partial season that otherwise would have got him to the 35/200 cutoff with a full season.
Factors that might get a pitcher with less than 35/200 might be injuries or strike shortened seasons. Maybe midseason callup would qualify. It probably helps if the pitcher in question has a track record of high inning totals. Strat might "grandfather" in a pitcher who had been an * pitcher for a decade and then had a GS or inning dropoff.
Bottom line in the end it is a judgement call by Strat. So for all I know if I worked for Strat and was in charge of compiling a season's ratings Feller being my favorite pitcher would be good enough.
While on the subject of judgement calls defensive ratings have historically been a judgement call. Many years there have been suspicions among Strato Fanatics that Yankee players got generous ratings.