The author of that list seems to be taking a very black and white view of praise vs concrit. Praise isn't just saying "ZOMG loved it!!1!" and concrit isn't just saying "This is what didn't work." Useful concrit includes praise. Knowing your skills is just as important as knowing where your writing needs work. And praise can be just as detailed and helpful, i.e. "I loved your characterisation of X because..."

I remember being taught the sandwich method of concrit. That is, begin with something you liked or some praise, then offer some suggestions for things that could be changed, then finish with something positive, possibly a summary of everything you liked. Basically, you sandwich any concrit between praise. Since then, it's become my favourite method of concrit. There's something very powerful of beginning and ending with something positive.