Their argument is that it'd save roughly $200K a year in travel. This is based on the fact that most northern teams spend the first few months traveling south. I have no clue how much it cost to keep players on campus. But I know a lot that stay for summer courses each year if they aren't invited to a major summer league. I believe they kept whatever financial aid and rooming agreements they were under throughout the rest of the year.
I think it could also align with the likely cut of minor league teams. Instead of a Rookie League Team...maybe just have a month long instructional period. One hurdle I see is that a mid to late July draft is when teams are traditionally looking a trade deadline moves.