I'd say that there is no functional difference between the tags. As for the concepts, formally, total synthesis is only a subset of synthesis, as the first two sentences of its Wikipedia article explain:
Total synthesis [...] usually refers to a process not involving the aid of biological processes, which distinguishes it from semisynthesis.
Given the ...
I think erratum already fulfills this purpose. From the tag info:
For questions that deal with possible errors in a specific statement of a specified book, article, website, etc. These questions should always include a complete reference.