Based on my experience that high school number from Top 96 is very low.
Just went back and looked at our tryout forms for last year, we had only 1 kid below 70 at our varsity tryouts. Comparing their exit velocities to performance in the game, we only had one kid in the 70s hit for any power last year. We hit a relatively high number of homeruns in the BBCOR era last year (22), and only 3 of them were by a kid w/ less than 80 on their initial exit speed testing.
A few years ago, we had a kid who hit 45 varsity homeruns in 4 years, and by the time he left as a senior he was at 98-100 with wood.
Again, a high exit velocity doesn't mean that they can hit. It shows the kind of damage that they might do if they can hit, and it shows players who will probably struggle to hit unless they have a very high hand/eye coordination and square the ball up more than most hitters.
Exit velocity is a nice tool, but obviously just a small part of the evaluation.