It makes you wonder if a Dad like that knows pitch after pitch if the velocity is consisently the same, and if he knew what a 94mph fastball actually looked or felt like that even he would notice such a huge jump.
I think it would be fair to say that most of us couldn't or wouldn't notice a big change in velocity if his kid threw a few around 84 or 84mph. I don't think 3-4mph is that easily discernible to notice for us laymen. To PG it might be. lol. But I will say that I remember watching Nick Fuller throw at East Cobb a few years back and he was hitting 94mph like it just another day to him. 94mph will make the hair on the back of your neck stand up!
PG, my dad is that guy you refer to that just sits there and guns pitchers just for giggles and his own pleasure. He doesn't bother a soul nor use his gun to make it known how kids are doing. Since his grandson was a pitcher he just wanted to learn more about pitching, velocities, etc. and had a couple extra bucks in his pocket.