Ive heard of that old rule eoc but truth be known there are a lot of CPL holders I wouldnt send my family with.
As you said though, one needs to be confident that they could justify that everything had been done to standard, and possibly in a court of law.
More importantly though, as my old CFI used to say, be sure that you would be able to sleep at night if something were to happen. If you are blaming yourself then you aren't likely to be able to convince others not to blame you.