Just to clarify, sunlit isn't answering your actual question about what makes a cryptocurrency coin a security, it appears he is confusing securities laws and money transmission laws (which is kind of easy to do, since many articles published on the two subjects don't draw a clear line). I deal with these rules almost daily, and there's been times when it happens to me too.
The most applicable rule for whether a cryptocurrency is considered a security by the SEC is called the Howey test. I don't want to go into that much further here, but you can get a quick overview by googling it.
The issue he seems to be referring to revolves around "stores of value" and rulings and guidelines from FINCEN (the US regulator in charge of things like money laundering). But this is a totally separate issue from securities law.
And, yes, you're not really wrong in what you said, some mined forms of cryptocurrency have been ruled to fall outside the guidelines of security law, and this especially tends to be applicable to older cryptocurrencies (which were mostly mined). But this is part of a big topic, so more info some other time.
Thanks for that, I look forward to your next posts