Someone, we'll call them Bob, goes to all the trouble to build the binary, finds out that it doesn't match with what the app store is distributing then just shr

Someone, we'll call them Bob, goes to all the trouble to build the binary, finds out that it doesn't match with what the app store is distributing then just shrugs their shoulders and uses it to connect with other users in a secure messaging network because their binary is correct? What could possibly go wrong?