Blame it on the boogie. It's just a bit brighter and louder and has a funkier feel. But I guess 1978 vs 1973 disco had evolved further.
Yep Dancing Machine was released in 74, but it was made in 1973 - in fact its on the 1973 album Get it together, and was only given its own album when it blew up around March 1974.
Dancing Machine comes real close, as its great song too and was the first proper foray into Disco for the J5, plus its Michael's first semi adult sounding vocal "Dooo ittt babbby - automatic, systematic, self contained"
Michael debutted the dance step - the Robot in that song too. It did its job and revived the J5 after a few months of lacklustre songs and chart performances.