I have the ELEMNT app switched to not using mobile data.
During a ride if the phone is on a mobile network I still get messages popping up on the Wahoo Bolt. But for long rides I tend to switch to airline mode so that I can enjoy the personal time, just using data at the stops.
Is there a reason why you need the app to be using mobile data? Maybe just switch it to using mobile data when you need to upload a ride without wifi?