Marner got a bonus deal from Lou last year. So it's just rumours. It's more likely Matthew's agent is being a dick as they all are to the Leafs.
The story I heard on radio was that the bonus deal was promised to Marner before Lou got here. He honoured it but made it clear that it (bonus based on individual's performance) was not something that he would have approved.
It makes sense to have any bonus structure done based on team success rather than individual's, especially for rookies, but if it were true that Lou is the only GM who's stubborn in this stance, then it's gonna be a problem.
Apparently MacDavid got approximately 3.5 Mil last year and Lanne just got about 2.7 mil from the Jets. It would not be unreasonable for Matthews to seek a deal somewhere in between.
Apparently the last time a top 10 pick didn't get the bonus was Larsson in New Jersey when Lou was the GM there.
If all the above were true, it makes the Leafs look bad, and they're trying to lure free agents like Vessey.