Some of the best lessons I learned in this business were done exactly that way where it was sink or swim time.But the important thing is who taught me and how they approached it...and each person is an individual,so that has to be taken into account.
In my late teens and early 20's,I would naturally get a little upset if I was corrected,but that's youth talking and immaturity.You think you know everything,and then you look back at 30 and you feel some shame

But a few seasoned cooks and chefs would make me work on weaker points in simple ways that stuck with me.They weren't negative or nasty,but you knew by the tone of voice that you had best pay attention.
Say if I needed to speed up and get more done in a shorter time,I would be given a time limit.Since I respected these people and wanted to earn theirs,I'd really push to get it done.From that I learned how to prioritize.Every once in a while,they'd shout out the time that was left and that was all they needed to do.
Or when the chef would run expo and they would really ride me about ticket times...down to seconds.But I knew enough to understand it wasn't personal and the way to get them to stop was by improving.
And people need to learn how to be comfortable working a station alone.They have to do it sometime! If they aren't comfortable with 5 tickets,how are they going to deal with a busy night or lunch service with a lot more than 5 and it's just them?
Now,if you can see that this person is going down badly and the flop-sweat is all over their face,yeah..help them before they start to panic,but if they are doing good on the ticket times,let them learn and get into the mode where they get used to multi-tasking.
But if they get upset? They can go find work elsewhere if it's that much of an issue and you've tried every incentive to get them on the same page.It's the chef's kitchen and you do what they want...good or bad,right or wrong.
I disagree with my Exec from time to time,but it's HIS kitchen and his reputation and he's a wonderful guy,so a few differing opinions here and there don't affect my loyalty or performance.