Whitlock is a very rare case. They're in a situation where they have to keep him on the big league team because he's a rule 5 guy but they also have to be careful with him because he just recently had Tommy John. Right now, I think they care more about him being on a starter's schedule as best as possible. They're not exactly stretching him out but they're usually getting at least an inning plus from him, the one-out appearance was rare yesterday.
I'm not sure if they plan on ramping him up later in the year, or if they want to save him for a playoff run where they feel confident in using him out of the pen more. It's a good problem to have because of his talent level, but the downside is it either leaves us a pitcher short in the pen or a bat short on the bench and we've seen that seesaw all year.
I really hope Whitlock pans out, develops, and exceeds ALL expecations. I hope he's pitching 200 innings and winning Cy-Youngs and we can go shove that in all the Yankees fans faces. But, we'll probably have to wait a year for that to happen.