The note reads:

"When sharing files with Fast Share between two Pixel 4 devices, the operation completes successfully, but the UI on the device which receives the file states that it did not receive the file."

The first reports about the sharing capability that surfaced in mid-2019 referred to it as "Fast Share." And while the note also calls it by that name, a more recent sighting of the feature by XDA Developers showed that it had been renamed to "Nearby Sharing." Whatever it ends up being called, it'll give you a way to easily share files with fellow Android users in close proximity. Google has yet to reveal when it will roll the feature out, but it's expected to make the sharing capability available on the platform's older versions, as well.