I doubt this is reason. Vin was like this 5 films ago with him. It has to be another reason. Considering they are close I'll say Vin probably wanted something in the film that Lin said no to.
Letty had big following tho. I remember all those bring back letty petition and people were send massive emails to Universal that the studio even responded. I remember that cause I signed it lmao. She was the original Justice for Han.