Does it really block cookies?

I am just another plugin user and do not represent the plugin authors. Since your question is probably the most common one found on this forum, it might be nice if there were some clarification in the most visible manner that this plugin does NOT block writing cookies. That is NOT the purpose at all.
What this plugin does is to provide a controlled method for deciding to write certain cookies, based on the visitor’s selection of various options. To work as intended, the only place in your entire site where a cookie gets written is in the place in the plugin intended for that purpose. If you have code anywhere else at all to write a cookie, the plugin knows nothing about it and has no control over it.

I think what people are often wanting is a plugin that hooks the low level functionality that reads and writes cookies and decides what to do based on what the visitor has indicated is her or his wishes. Alas, I don’t know of a plugin that does this. But that does not change people’s expectations.

From a practical perspective, all this plugin is really good for is the management of the worst sorts of tracking cookies, insofar as the web site owner deliberately sets out to use them, but wants to give visitors a choice. Which is very nice and helpful! For all the other cookies, such as those technical cookies inherent in the use of WordPress or PHP, or the cookies managed by third parties, this plugin is not doing anything.