I've written a question along the lines of "How does WhatsApp's View Once feature work", where I ask what the existence of such a feature implies in terms of API offered by the OS and used by WhatsApp.
I'm not going to ask a generic question about design principles, but a question about how WhatsApp (well, some aspect of it) is designed and what the OS on which it runs has to support for that feature to be possible. Specifically, I'd add code snippets to explain what my hypothesis is, in terms of what functions I expect the OS to expose and what WhatsApp functions would make use of those and how.
Would this be an on-topic question? Or should I maybe ask it on Software Engineering?