There was rumours last year mcdavid was unhappy having no one to play with on his line and requested they give him Nuge.
If true, that is disappointing and makes McDavid's "team guy" persona seem like a bit of a fraud.
I just looked at the numbers, and he had 12g-22a-34p in those 23 games since Yamamoto joined the team on Dec 31, 2019, which is basically identical production to what he had before that (22g-41a-63p in 41 games).
The team was 20-17-4 before Yamamoto came up and 17-8-5 afterwards. So the team went from 88 point pace to 107 point pace. There are some factors like improved goaltending after the awful stretch in December that contributed to it too, but McDavid produced the same and the team won more, so I'm not sure what the problem is.