In all honesty I don't understand your post. Neither Matthews nor Nylander have played on the first PP unit since they joined the team in case that's part of your point.
That's slightly disingenuous.
The PP time is pretty much distributed equally.
2016-17: Matthews 2:27, JVR 2:24, Marner 2:23, Bozak 2:22, Nyalnder 2:21, Kadri 2:11
2017-18: JVR 2:17, Marner 2:12, Bozak 2:11, Matthews 2:09, Kadri 2:05, Nylander 2:01
2018-19: Marner 2:26, Tavares 2:26, Matthews 2:23, Kadri 2:15
2016-19: Tavares 2:26, JVR 2:21, Matthews 2:20, Marner 2:17, Bozak 2:17, Nylander 2:11, Kadri 2:09