The EU is negotiating on the behalf of future and current Schengen area members. While you have numbed it down it is simply that the Visa Waiver Program is tou

The EU is negotiating on the behalf of future and current Schengen area members. While you have numbed it down it is simply that the Visa Waiver Program is tough on Romania and Bulgaria and also has a fee for the ETA whereas there is no such thing to go to the Schengen area from Canada or the USA. So yes it does have to do with Schengen, but not the treaty specifically as it doesn't involve inter EU travel.