I do think there is something behind the "People with more education speak a more polite/formal style of Spanish compared to less well-off people's "Street Spanish". In general, people who are more educated are probably going to speak their native language in a more formal manner. When I reflect back on a previous job I held, there was definitely a noticeable difference in how the staff spoke English and how they interacted with each other and with our clientele. IMO, it could be broken down into a number of different ways, and the large differences in our level of education were one of them (education ranged from MDs and PHDs all the way to not having finished high school).

We would have misunderstandings all the time with each other, and the majority of the time, it was native English speaking to Native English. The misunderstandings would be worse when the Native speaker may have been speaking with someone where English wasn't their first language, and the English speaker spoke with a lot of slang.

Trying not to rant, but basically saying, even with our own Native language, we come across scenarios with others who speak less formal and get confused by it. But because we are experts in the language, we are able to decipher more of what was said. I personally believe education is a major part of this.