The Spoon metaphor is quite helpful when the team(s) you work with have an understanding (I like team Social Contracts just for this reason) about the usage of this phrase to signal something that means "give this person some space and time and ask if you can take anything off of their plate in the interim."

What makes the Spoon metaphor work, though, is having a team/organization/corporate culture of Trust over Fear. This is key because in a culture of Trust, we assume the best intentions of others and look for ways to help and support those needing it. In a culture of Fear (which can look subtle or overt, depending on the culture), the Spoons metaphor could be seen as someone not working as smart or as hard as others and an indicator that they're a weak link in the team. In the latter, a person may be hesitant to use the Spoon metaphor because it might be viewed as a career-limiting move.

Still, the concept is valid and the application sound when there is trust.