The question is: does this bring any of the purported benefits of the Semantic Web? Does it suddenly allow "agents" to understand the meaning of your web pages,

The question is: does this bring any of the purported benefits of the Semantic Web? Does it suddenly allow "agents" to understand the meaning of your web pages, or are we just complying with a set of pre-defined schemas that predefined software (or more specifically, Google, in practice) understands and knows how to render. In other words, was all the SemWeb rigmarole actually necessary, or could the same results have been achieved using any of the mentioned simpler alternatives (microdata, OpenGraph tags, or even just JSON schemas)?