That might not work because some employees might find that the volatility is going to be problematic for them because most employees want their investments to be stable and will be certain to give them money when they retire.
That's why the keyword here is
"option", well if you don't like crypto's volatility then you opted out.
Behinds if you really wanted to invest then why not go directly buy bitcoin in an exchange and have it in your hardware wallet, at least you have total control of it.
And regarding the article, this is released on Feb 9, so I don't know if it is still being offered as the price plummeted since.