Doesn't exactly come as news that Apple has Ios in an iron grip. They might not have a monopoly, but they certainly have a level of control that Android doesn't.
iOS is their own product. Every company has its own products on an "iron grip", as well as controlling who gets to partner with them (and e.g. sell something on their platform).
If Microsoft had just a small share of the Home/Enterprise market with Windows, they'd could close it in any way they want, same way the game companies do for their consoles or Apple for iOS.