The Phillies might be taking an approach where they develop most pitchers as hybrids the first couple of seasons. 2-3 inning outings at most except for a handful of top prospects. Then once they have seen them for 50+ innings (and in the spin lab) they decide whether to develop them as starters.
Roster rules are much looser the last couple of years with that development designation. Maybe 5 years ago they started to piggyback in the lower levels. Now it is as if they have 3 multi-inning pitchers per game sometimes and just move players on and off the roster as needed. The only limit is the 180-player limit. All other roster limits are for game days so effectively we have 30 guys at each level and more hanging around the Clearwater teams.