Hi Jarom,
The Survey123 field app does not support landscape mode on iPhone or other mobile phone devices, only on tablets, such as iPad. Therefore even in camera mode the app will be acting as if it is in portrait mode when the image is taken.
Out of interest, what version of the app are you using? We have made improvements to camera image rotation in the upcoming release of Survey123, version 3.5, so please check it out later this week, or try out the 3.5 RC version available on EAC.
Phil.