By objective measures, Ehlers and Scheifele have been the Jets two best and most productive top 6 offensive forwards at 5v5 not only this year, but for a couple of years actually. They are the line drivers.
I can see two (rational) reasons for Ehlers getting less TOI than *Scheifele's wingers*:
1) Being the line drivers, Maurice wants Ehlers and Scheifele on separate lines (like Kane and Toews have been mostly separated AFAIK).
2) This is my own theory
I am sometimes wondering about Ehlers endurance.
I have seen (visual) signs, that he seems quite gassed in the end of a single shift, a game, and maybe a season (I haven't checked stats to see, if it is backed up).
Being an extremely explosive athlete, it could make sense, he may not be the most enduring player?
So, maybe Maurice is seeing/knowing something we don't, and is careful not to overplay Ehlers, because based on impact on the game, him and Scheifele should certainly play the most at 5v5.