Auto activity start option showing up in Garmin connect app

I posted this in the iOS connect app forum also, but I thought I would as here as well.

I recently got a new iPhone, so I re-downloaded the Garmin Connect app. I noticed under activity tracking options (device settings in the app) there is an option for auto activity start, like on the vivosport, etc (not move iq). I tried turning it on and syncing, but it just turns itself off.
Does anyone know if this is going to be a feature of the Fenix 5, or maybe an error on Garmin’s part in the app.
I just find it strange that the option is in the app but the device doesn’t support it.
I am wondering if anyone else has this setting option in the connect app with a Fenix.
I have an iPhone X, iOS 11.2.6, latest Garmin Connect app version.
???????Thanks.