It is an interesting article that raises a few questions for me.

Since timing is an important part of general musicianship, and rhythm is a basic element of music, it would seem that players of nearly all musical instruments require similar special neural development in their brains as drummers, and maybe more in some cases.

Memorizing scales and chords and playing them on a guitar or piano ... or an organ with foot pedals and multiple manuals.
Or check out what a pedal steel guitar player does!
By drummers, I wonder if they are they meaning rock drummers specifically? Tabla drummers of India and tombak drummers of Iran etc, do not move all of their limbs like a western drumset player but mostly just fingers and wrists like a piano player.

Musicians playing AfroCuban/Latin music play with awareness of two times, related by a 3:2 ratio, simultaneously. The basic 'son clave' pattern illustrates these two tempos ... three slower beats followed by two quicker beats. And then there's salsa dancers .....

I don't think it was mentioned in the article if the non-drummer test subjects were musicians or not.
Drummers indeed have grown special brains, but how much do they differ in that respect from other musicians?