2. If deleted data not being purged from your iOS device is a "significant security flaw" then you shouldn't be using a device from Apple or Google; your threat model is way beyond the two big players.
3. Hyperbolic comments[1] don't help issues being re-opened. Helpful comments, preferably with steps to reproduce, and a polite note that the issue is still current, will get the issue re-opened in my experience. Getting on your high horse and making silly claims would get you put to the bottom of the pile if it were my job.
[1] https://github.com/signalapp/Signal-iOS/issues/4916#issuecom...