When we start to think of ourselves as someone with a certain status we get much less receptive to criticism from those we perceive as the same or lower social status.
This can be consciously corrected for but takes some effort and practice.
I really think this is a poor phrasing as it has negative connotations. Same with “brutal honesty” which is often used as an excuse to throw out empathy.
Treating people well is not at odds with being honest and clear. If anything, it’s kinder to bring up issues early, no matter how painful it might be.
My observation had been many people who become managers lack the necessary social skills to do a good job. They do not have the context to understand what not “sugarcoating” actually means. Instead they take the easy half the advice and implement it badly.
To an adult, failure is a reason why could be fired, or something that loses them the respect of their peers, or proof that their imposter syndrome was right all along.
Ultimately it comes down to receptivity of the audience. Some people cannot listen, a cognitive impairment, such as Dunning-Kruger. In this case it doesn’t matter what you say because they hear: I’m awesome. Don’t waste your time.
Be direct and be deliberately honest. Do not soften the blow. If the product is complete shit then start with that. Then find the merits, opportunities for improvements, and provide guidance for the path forward.
For some reason, contrary to all expectations, this is so much easier and effective with children than adults. Children seem more inclined to learning and a willingness to accept productive feedback while adults are more inclined to filter commentary and simply stop listening.