My one quibble with this example -I sincerely hope there was feedback given the entire duration of those six months. Being told far after the fact that you are doing X thing poorly is a kick to the self-esteem.
Oh absolutely, it was pretty clear that this person wasn’t on track 4 weeks in. And after that you have to keep communicating that we were expecting more progress… what are the issues will you make the deadline etc.
"You should have been able to finish this in 2-4 weeks, but it took you 6 months. What went wrong?"
That's actually useful feedback, I think. It highlights that the giver believes the recipient has abilities that exceed the demonstrated result.