Low end pads don't have the gripping power as Kool-Stops therefore there's less brake flex. You're right though, he won't have the same stopping power.

Example... black threaded Kool-Stops are grippier than stock Dura-Ace "8-speed" pads. the K-S pads cause my aluminum forks to flex under braking more than the DA pads do but... I can stop quicker but the visible effect on the fork is a little spooky.

Another example... low-end MTB brakes (the stamped steel ones with sloppy pivots) don't work well with the K-S MTB black pads due to pivot play and the extreme flex in the brake arm. You usually have to use a less grippy generic pad or the customer will complain about the noise and/or vibration.