it does exactly what it should.
then, since the css is linked to each block, it can only be set on him
the flaw is that you cannot set it on all blocks with the same class. but I don't think it's designed for that.
I was tired of adding custom classes to blocks and keep track of all my custom CSS. I searched on Google for some way to handle CSS for all blocks easily and I found this gem.
So simple idea and really useful!
I make reusable blocks and style them with this plugin, saves me so much time.