Would agree and disagree..normal routine, be who you are, do what you do those present will always see what they want to see - including their own biases and their own needs and quirks.
That being said...we can talk all we want to about mechanics, and mental attitude, pitch command, and getting batters out....but having been through scores of these things and having debriefed scores of recruiters and scouts...there are what I call "Qualifying velocities" for each level of ball. (MLB, DI, DII,...) You don't make that velocity you will simply not be considered at that level. No matter how well you ply the craft.
Case in point...Watched a couple prospects who we'd watched for years, at a showcase who simply rared back at the event and threw as hard as they could to get their velocities up. Hit batters, walked players, threw in the dirt, and on that perfromance were invited to national events simply due to "qualifying velocity". Both ended up with big DI rides, one has command the other still struggles to find the plate but has a velocity that makes schools drool. Other clean pitchers at the shcowcase with finely crafted motions, who simply got players out were ignored.
We'd all love to believe that beautiful mechanics and an ability to get batters out counts, and it does, but only beyond a qualifying velocity.
Do you overthrow at a showcase? No, absolutely not. but be aware that velocity does matter and it is worth throwing a couple ball to "touch" (not my term, a scouts term) a qualifying velocity.
Here is another thing to be aware of...many Scouts will judge your future velocity in part on the basis of your running speed, no, really.
Without going to far into physiology...to scouts footspeed is very indicitive of a high percentage of "fast twitch" vs. "slow twitch" muscle fibers, fibers that are in part responsible for creating velocity. Don't underestimate the importance of your 60 time, even if you are a pitcher.