I'm not familiar with MLB, only with NBA. But even their "ad-free" really isn't - there are still ad banners inside the arenas, on the court itself, and on the jerseys, the announcers often read ads ("this segment was brought to you by ..."), and if there is arena feed during the regular breaks, the in-arena events like a half-court shot are often sponsored as well. Plus there's standard service ads that announce next games.

Unless MLB blurs/bleeps all of these, it's not really ad-free.