I disagree: If I assume that anyone is struggling all of the time, then I cannot prioritize assistance to those that are actually struggling - which means that those that are actually struggling loose out.

I agree that it comes with vulnerability and risk. However, I believe that the way out here is reducing the risk, by building team structures where people can talk about these issues without being punished for it. That is: Teams where people are not expected to be robots and interchangeable, but humans with strength, weaknesses and temporary or permanent challenges that need addressing.