I don't see it in the Android app either, and I find the original claim very hard to believe in the first place, since that would be a weird piece of information for Signal to reveal about a user.
Apologies for the mistake. I'm running a Signal fork called Molly[0]; the feature I mentioned seems to be unique to that fork, based on a search of the code.
However, it shows that the data is being provided to the client by the server, in some way. This is a guess, but it may be because sending clients have to encrypt with a key for each device.
