I think this reflects how fluid scouting evaluations can be, especially for pitchers. For NFL or NBA drafts, the drafts are 3-6 months after guys have last played in regular games. But in baseball, guys are playing right up until the draft, and pitchers can improve their velocity/slider/delivery late in the year, sometimes significantly so. It's probably not rare for a pitcher to be throwing a bunch of 95's in May when they may have been maxing at 92 in early April. Or to have a good-looking slider in late May when they were throwing a crummy slurve in April.