I think Knies absolutely has the potential to be a solid penalty killing option at some point, but maybe it's a little early in his career to be throwing him into those minutes. He's been on the ice for 4 goals in just over 8 minutes of PK time. That's a GA/60 of 28.46, which is more than any other player in the league who has played 8+ PK minutes. There's probably some noise/small sample stuff at work there, I highly doubt he continues to get scored on at that rate. But there has been times where his inexperienced has shown on the PK for sure.
I get trying him in those minutes because of his potential and the lack of other options, but with Holmberg in the line-up now he should be able to handle those secondary PK minutes and if not I'm pretty unsure what the point of Pontus Holmberg is.
Knies should also be getting PP2 time over Jarnkrok, it's actually kinda baffling that hasn't been happening this season.