the attribute was added in this PR, and there is some discussion about it in the comments (well, some related-sounding things at any rate; though i can't say i follow it all). there's also some discussion about it in this pitch thread for custom executors (Chris & John discussion starting here).
the final attribute is marked as ABIBreakingToAdd | ABIBreakingToRemove in this source file, which suggests it can't necessarily be freely adopted/dropped. additionally the output of this godbolt example suggests its presence may impact type metadata and descriptors.