Sure, that’s the standard of care legally. I would contend that the real question, however, is really whether or not that’s reasonable. For example, consider me:
I probably practiced for about fifteen years not knowing that ASTM C926 existed with a deflection requirement.
About fifteen years ago, I discovered ASTM C926 because I got frustrated trying to chase down all of the various serviceability requirements and finally found a book in which a bunch of them were aggregated.
I subsequently re-forgot that ASTM C926 until you brought it up here because it simply is something that is never, ever discussed by humans in practice. Am I a negligent structural engineer? I don’t feel like I am.
Consider that the requirements of ASTM C926 will usually create an obligation for me without any human being having personal knowledge of my projects ever actually realizing that is the case. Rather, an architect will select a component from some masterspec database and that will trigger the reference to the ASTM spec. And then I’m on the hook, even though the only humans to have given consideration to the issue are the ASTM authors and, indirectly, the folks who created the masterspec database, neither of whom are involved in my project. So, somehow, I have to retrieve all of the relevant project information from robot land and ensure that I, a mere human, have it all covered.