They didn't sell the movies to Universal, it was a carriage/streaming rights issue, similar to what Disney had to do with Star Wars: The Force Awakens with STARZ. Warner had licensed the Harry potter films to Universal's cable/satellite channels USA and SyFy as exclusives, which prohibited Warner from making them available on HBO Max until a deal was reached.I never really understood why WB sold the right to Harry Potter. I can understand selling the theme park rights but, the movies? That's their Star Wars or Marvel.
Hairspray (2007) is in 5.1! The iTunes version that you can buy is still only in stereo.