Blockchain should be singular - "blockchains" should be used when referring to the technology in general. Getting this wrong is the #1 indicator that an article on blockchains isn't worth reading.
The word "blockchain" works just like the word "computer". You can have a blockchain or multiple blockchains, just as you can have a computer or multiple computers. And you'd refer to "blockchain technology" just as you'd refer to "computer technology."
I do hope you'll read the article regardless!