It refutes the notion that DMs read and understood the system.
Complaints that DMs are setting the DCs too high, using DC 15 as an average, are justified. Because that means they read the system and are using it.
Complaints that DMs are setting DCs for things that are explicitly not covered and don't require checks are just complaints they didn't read the system.
The fact it keeps coming up as an example is more a tale of DM horror stories not knowing the rules. Not tales of system horror stories due to it encouraging DM arbitration. Or system horror stories of how the system math is broken.