This is the most misunderstood parenting advice ever. To the point that yes, parenting classes teach it incorrectly. It is not praise that is de-emphasized, but connecting the praise to their value as a person. You do not want to say, "You are a good child because you achieved a good result." You want to say, "Good job for putting effort into X", regardless of the result, because even if they do a bad job at something, they are still a good person.

"Praise is bad" is a gross over-simplification of the recommendations.