*He hears a difference but doesn’t feel it’s a "life or death" difference.
*He fairly certain it’s not due to diodic effect.
*He cannot explain it except that it’s not due to diodic effect so simply move along folks, nothing to see here.
How nice that he can relieve us of this "life or death" burden.
Here is a related article on the matter dealing with objectivity vs subjectivity. What I like most about it is the shot of a t-shirt that states:
I am an engineer. To save time, just assume that I’m always right!
All the best,
Nonoise