It didn't.

Although Geoffrey and folks considered a rewrite of the compiler along the lines of Michael Ficarra's CoffeeScriptRedux, they decided it was more pragmatic just to work with the existing compiler and get it to produce Modern JS instead of the Lowest-Common-Denominator JS it previously output.

A wise choice, especially given 2017 interest and energy levels.

Edit: To be clear, to the extent anything can or can not be considered official in open source, Michael's project was his project, and never made it in to the main repo. We encouraged it just as we'd encourage anyone to try and make an independent implementation — but CoffeeScript has never asked for financial support.