You are correct but that is only when the Class R rejection fuse clips have been installed in the safety switch. There are many 30A devices that do not even have provisions for Class R fuses (especially pull out designs).
Also, the above mentioned favorite Type S plug fuses rated are only 10KA max.
It is not fair to "bash" all miniature breakers because of the old Zinsco and FPE problems. A comparable bashing of all fuses would be to look at the renewable link and standard plug fuse over sizing issues.
In reality, other than Zinsco and FPE, how many 50 year old breakers have been found to not trip? Yes, I know there are many that wouldn't reset but they still protected the conductors.
I remember something about an unofficial study some UL engineers did back in the early 80s. They went to their own houses and removed their load centers without disturbing the breakers. They then ran normal overcurrent tests on these breakers and found no appreciable loss of the original tripping characteristics.
And yes, I know there are different tripping characteristics between manufacturers and tripping elements, some breakers are "faster/better" than others. But I have never seen any factual indication that miniature breaker characteristics are inherently degraded by age.
