What makes the allow "celluar data" setting appear in the settings of an app under iOS13? Is it directly related to the presence of networking code at compile time? Or does it appear later, when the app tries to connect to the internet the first time?
Can the absence of this setting be a trustworthy indicator that the app does not access the internet via Wi-Fi oder cellular?
The mobile data option appears in setting after the first time your app actually uses mobile data. It is enabled by default.
The option not being there could imply that the app has not used it, but it would be better to check the level of data usage on a per app basis further down the mobile data page in settings.
Credit to this answer.