Here’s another way to look at it: a guy who isn’t the biggest ba’al middos is coached to do all the right things so at least he’ll look like he’s trying (perfectly legitimate). A really decent guy, maybe a little nervous/inexperienced, forgets and messes up.
Logical outcome of this – by making a big deal out of it, we are actually invalidating it as a criterion to judge by. Like when someone calls for shidduch information, and you are forced to exaggerate and misrepresent the subject in order to accurately portray them. It’s a bissel counter-intuitive.