This comment seems unnecessarily mean-spirited... perhaps I just feel that way because I'm the person on the other end of it!
I agree the code you have there is very readable, but it's not really an example of what that sentence you quoted is referencing... However I didn't spell out exactly what I meant, so please allow me to clarify.
For me, roughly 5 calls in a chain is where things begin to become harder to read, which is the length of the example I used.
For the meaning of "multiple", I intended that to mean if there are nested chains or if the type being operated on changes, that can slow down the rate of reading for me.
Functional programming constructs can be very elegant, but it's possible to go overboard :)