You are lucky to have someone write requirements who weights in these aspects. I have seen too many specs (this mostly happens in business software) where failures are knowingly or unknowingly ignored... because schedule.

I think failures should be designed for (or at least explicitly defined) even if the requirements do not include them.

I think that's a lot more common in software where safety matters. Often such software is developed according to some regulations like ISO26262.

Yes, I have to constantly remind other front-end developers that we don’t need to be pixel-perfect faithful to Zeplin or the story. It is more of a guide and you can always bring up any concerns you have or if you think something should be done differently and we can talk about it.