Microdata parser does not catch all markup

[teledyn]

I hope I'm using this correctly, but I notice when I issue the following

g = Graph().parse('https://blog.teledyn.com',format="mdata")

I get back only 6 triples, 3 of them just for defining an rdf list for the single Blog element

On the other hand, inspecting the file in Google's testing tool, there are microdata tags for the two BlogPosting items and their contents etc that the parser has missed

https://search.google.com/structured-data/testing-tool/u/0/#url=https%3A%2F%2Fblog.teledyn.com

is there something I'm missing in my parse statement?

partially related to this, I find if I include the PublicID= mentioned in the help(g.parse) doc, it has no effect in rdfa; not a big issue as the properties can be copied, but is there a trick to overriding the base URI in all parser formats?