Looking at this thread, you’re asking the right technical questions, but here’s the reality: Most “text interceptors” are just glorified notification readers that grab what pops up on screen before kids dismiss it. They can’t crack WhatsApp’s encryption, but they don’t need to - they just screenshot notifications or use accessibility services to read messages as they appear.
Kids figure this stuff out fast though - they’ll spot battery drain, weird app permissions, or just switch to apps like Signal or Telegram that parents don’t monitor.