If he chooses to ignore it, then he doesn't understand the correction. Does not a correction communicate: "What you are doing is wrong; I want you to stop what you are doing right now." If the dog does not respond to that, then he does not understand that.
I'm on a quest to find out if a high drive, working line GSD could be raised with +R reinforcement. I am 90% confident at this point that not only could such a dog be raised that way, it would likely be among the most the best of the best in the performance category. But statements about genetic "hardness requiring a firm hand" kinda scare me a bit. Could such a statement indicate a lack of biddability? Or is it simply bad training?
RATCHX3 High Jinks vom Neuanfang - Gotchya Day: 1/23/2013 DN, SG, SR, CA
Inspire Spark to Ignition! (Ignite) Gotchya Day: 10/8/2016
C-ATCH Pimg - RATO, UJJ (x2), DJX, HIT, CA, CGC, High in Games, Reserve High in Standard- CPE Nationals 2014