I think it's a significant change in angle. These variable-V-pulley transmissions are used in hundreds of applications, perhaps the most common of which are washing machines, which during the spin cycle must accelerate a load of wet laundry from zero to fast with a smallish motor every few days for years. They're also used in tiny diesel cars that you cannot buy in the US, but which have been popular in Europe and I want one.
Clearly further research is needed, and perhaps a website that features discussions and tutorials on industrial power transmission would be a good place to start. I haven't tried it, but maybe the Google search terms "Industrial V-belt wear" might help.