I can understand that if they didn't compile it themselves they don't want 3rd parties using the 'Signal' name.

The name is what their reputation is staked on, and if a third party compiled it they have no idea if malware is secretly packaged in there too.

Having said that, the smart move is to dedicate a few engineer hours to packaging it for every linux distribution and every app store, even the smallish ones, to prevent others trying to 'be helpful' and requiring you to send a takedown.