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.
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.
Here's the code:
https://github.com/mollyim/mollyim-android/blob/26403ab1806a...
https://github.com/mollyim/mollyim-android/blob/26403ab1806a...