Typically, the pen (if you have good stuff) leads to lower era for "failed" starters. Also, he mostly started but didn't normally go 5+ innings so it would be no different than an opener. I will bring it back to Adams last year, when he was going over 2 innings, he started giving up more hits and runs. If he can be limited per outing, I think you will see better numbers.
ERA per inning
1st inning 3.13 ERA
2nd inning 4.70 ERA
3rd inning 4.65 ERA
4th inning 5.06 ERA
5th inning 3 ERA
6th inning 0 ERA
7th inning 0 ERA
8th inning 0 ERA
9th inning 54,55 ERA
Now if you look at first inning of work 3.09 ERA, second IOW 4.5 ERA, third IOW 4.42 ERA and fourth IOW 6.55 ERA.
I don't think you can take the high ERA in the 9th as he can't close games, as he was going into his 3rd(4th) inning of work. Quite the word salad to say overall he has been pretty good in 1 inning of work in the minors.