I'm trying to figure out if the person who wrote that doesn't understand how Congress works, or is simply being deceptive.

The only "myth" there is pretending that it requires a filibuster-proof majority to pass any legislation.

The truth of that "myth" was well established during Obama's tenure.

Nope.

https://en.wikipedia.org/wiki/Nuclear_option

They could have done that on day one.

Why the downvote? The Dems clearly had the power to use the nuclear option (and in fact they did use it later in Obama's term, so this isn't just theoretical).