Since Dahlin is willing to sign for Fanatics, I think it's safe to assume he's willing to sign autographs. If he was able to get a "no public appearance" clause worked into that deal - I'm guessing he's not eager to sign lots of them, and the fact that he has not signed for UD reinforces that.
What does UD pay per autograph to rookies? I'm guessing it's only a few dollars. $5 per??
If he's told them he's not interested in signing 1000s of cards (or stickers) and not signing AT ALL for such a little price - they're in a really weird spot.
Suppose they can get him to agree to sign a couple hundred cards for each of Ultimate & The Cup....and 1100 for SPA (FW, FW Auto / Patch). Let's just call it an even 1,500 cards - while I think most rookies are doing more like 5k.
Also suppose they have to pay him two or three times more per autograph than they typically pay rookies (let's say $15 per, instead of $5, but I'm really just making up numbers).
That won't have a whole lot of effect this year, but it could really hit them in the years to follow - if more and more big name rookies follow suit.
I know a lot of people grumbled about Eichel, Patrick, and Hischier being signed to Leaf exclusives... and not having any auto'd Rookie Cards.... but if you're talking about players who have no real love for this hobby, and see signing cards as something they're stuck doing - not something they want to do.... if Leaf is going to pay more per auto, and ask them to sign less - isn't that how they ended up with those three?
For the guy that played 1 game last year, and they now want him to sign 5,000 times - The extra pay cheque might be very welcomed. For the guys looking at it as a pain more than anything.... Dahlin could be setting a new precedent that UD might now like.