I was talking about in game EVs. Guys who hit 30 bombs in mlb typically have an in game max EV of 110+.
Max EV is not everything and there are plenty of bad hitters with high max EVs but if it is under a certain threshold power might not be "real".
Last year in mlb 26 guys hit 30 or more homers, 25 of them maxed at 110+ (and 22 of them 112+). So typically a guy who can hit 30 bombs can hit a max ev of 112+.
This is of course in Game EV, not those Tee EVs that is done in showcases.
HR in the MLB go out of the park with all kinds of Exit Velo numbers, from 85 to 115mph, If you get backspin you can get carry and don't need so much exit velo. Today's hitters need huge exit velos because of their emphasis on launch angle and a swing that produces it. It's why you see so many hits that are hit hard enough to go out but dive down due to the top spin line drives and fly balls more often produced.
Guys are really big and really strong and if they hit the ball right, it goes fast and far, but there were a lot of guys who hit 25-30 hr in years past who were not so big or strong and with a ball that is not so juiced. But they got carry. (pre steroid years)
It's just easier to project that a guy could hit a lot of home-runs if they hit the ball really hard. But I'm sure scouts are smart enough to know what translates from college to pros. Case in point...
Take the first pick in the draft, he spent all year at Driveline working on getting the ball in the air, and he got the #1 pick, but the scouts also noted he has a hole in his swing middle away because he's looking to kill the ball all the time and a pull swing gets tons of bat speed and exit velo but it's in and out of the zone so you need to always look middle in, (you can read his scouting report on the draft tracker). If he doesn't fix that, he will need to be a mistake hitter. Pro's can spend all day on the outside, they'll make a mistake here and there, especially when the emphasis is on 100% effort, but they'll stay away from him until he learns to adjust. The point is, the scouts know, but they also know it can be worked on.