Probably because I told him that in my experience the rolled threads are generally a little "looser" than cut ones. Additionally, a cut-thread pushrod is typically a little stiffer because the diameter of the pushrod is slightly larger (in a rolled thread, the material is pushed up to form the peaks of the thread; in a cut thread the rod must be as large a diameter as the highest peak of the thread).

Rolled threads work too - but IMO you are much more likely to need a fairly thick threadlock compound to fill in the gaps.

Gordon