Agreed.
...and (b) there is nothing on the COLB to indicate that info was altered from the original long form.
That's where it gets sticky. For clarity, let's refer to the original birth certificate as "the long form," and the now routinely-issued certification as "the short form." As far as I know, no one has established that there would be any indication of an altered or amended original on the short form. The statutes, IIRC, refer to the new original being marked "amended," but I don't think there's any reference to the short form being marked that way, and I haven't seen any examples of a short form so marked.
Similarly, none of the birther lawyers have ever established that Hawaii statute §338-17.8 - Certificates for children born out of State" - would necessarily indicate that the child was born in Hawaii. The statute doesn't say.
OTOH, Hawaii statute §338-20.5 - Adoption; foreign born person - does say that "The true or probable country of birth shall be known as the place of birth, and the date of birth shall be determined by approximation. This report shall constitute an original certificate of birth".
I'm not sure how other states handle adoptee birth certificates, but I do know that in Georgia, the adopted parents can opt to use their home address as the place of birth on the new certificate, irregardless of where the child was born.
What I'm getting at is the fact that the short form may not tell the whole story, since, if there's more than one version of the long form, it would simply reflect the information on the most recent long form.
The significance of that would only come into play, of course, in the case of a candidate for President.