The camp dates are outside of Canada Basketball's control as they're in line with the FIBA qualifying tournaments.
With respect to forcing players, that's an incorrect assumption. They voluntarily chose to be included in the pool of athletes that would be considered for FIBA qualifications tournaments. From what I understand with people familiar with Canada Basketball's plan was that they were upfront with the athletes as to the expectations and commitment required. Their college coaches had to have been on board for it to happen.
Per the article below when Fortner was hired, you'll notice athletes like Cass Prosper, Toby Fournier and Laeticia Amihere are not listed. Makeer and Lattimore are on the list, however they haven't attended any of the camps to date. Whether they're in college or a professional, they have the choice to decline.
www.basketball.ca