I agree that "No class names" may me interpreted as "you're not allowed to use classes" but the main idea is to have a CSS file that is very loosely coupled with your HTML that you can just drop in your project and style it quickly. You can add classes at any time. "No class names" may be correctly interpreted as "loosely coupled". I don't think it doesn't portray them in a good light.

It means that you don't have to use 'mb-1--success-large' and things like that, but if @chrismorgan's point is that they've just swapped that for meanings encoded in element names rather than class names (in many cases not the usual meaning) then I think I agree.