If he's only thinning at the hairline then there's no point in him doing the rest of the scalp, but he should be needling 2cm into the adjacent healthy hair. The point of this is because those healthy hairs send out signals that recruit stem cells when they sense damage. There's no point needling where there's never been any hair.
Im letting my bias from all the success cases i seen seem to do full scalp and recover in order of crown ,mid , forelock then temples on a long enough timeline everyone is thinning sort of even if they only dipped a few % i thought the 2cm in thing to mean just outside norward zone for most people.
Doing only the areas of most concern more than half's my workload so would be sweet but i worry im slacking if i do just norward areas 1 to 3 instead of 1 to 7 .
The one picture we have of this from them i cant tell if the day 85 pic is just longer hair with a parting or a increase in the forelock area density/quality that gave the guy confidence to sweep his hair sideways so much it made people think he had tilted his head out of line with the marker. Im hoping its the latter
