This proves nothing. Sure, it indexes the text, but that has no bearing on SEO. Most people using hidden text use it as a keyword stuffing tool, stuffing more relevant keywords into the page in order to get higher page rankings. A lot of SEO techniques and how Google views them comes down to intent. It's pretty clear using hidden text and other gray and black hat methods will be picked up by Google and penalized beca…
"So here You have it. Google can index (and indexes) hidden text and dynamically inserted text."
Then concludes the entire thing with something completely unrelated:
"If content is relavant [sic] to Your website, You won't get penalty from google."