Are fractions really threshold concepts?

The linked story concerns a maths professor who thinks that fractions can and should be abandoned (along with long division and some other topics) in early maths learning. They might be re-introduced after calculus, he believes.

I have argued that learning basic arithmetic consists of a series of obligatory threshold concepts, but I stopped at division. Fractions usually come next in the traditional school curriculum, and they too are regarded as a threshold concept; this mathematician obviously thinks they are not. Discuss.