One doesn't always have to do with the other.
Discussion
Capitalism means you get to choose where you invest. Apple's walled garden wasn't a problem until this, apparently. Lol. Me? I'll never buy a device that prevents me from running code outside their ecosystem.
Phones should be secure as possible, if you need an unwalled garden use a computer.
Security is great and all, but walled gardens are just another lackluster attempt at security through obscurity. It never works. Never has, never will.
Telegram's MTProto encryption protocol is a walled garden, and I would be shocked if the NSA weren't poking holes in it for fun. Signal's open Axolotl double ratchet, however- that shit is ridiculously secure. Walled gardens are moot.