The phrase makes a statement about recursion in general, no further narrowing it down to one kind. One cannot generalize from one case (non-tail recursive, which might have unbounded memory allocation) to the whole class of calls, which is recursive calls or recursion in general.

So it is not necessarily a true statement about recursion. It is only a true statement about non-tail recursive ones. It is an over-generalization. The docs would to well to distinguish those.