My phone is configured to only update apps over Wifi. If you're saying the iPad was tethered to a phone, then on Android you can configure a specific wifi network as "metered' which will stop things like updates using it - not sure if iOS has similar functionality or not. (Android will actually normally default to a metered network if it depends it's tethered to a phone)

I will admit I do sometimes turn on 'Data Saver" when using a non-unlimited eSIM, but more because there's no real reason not to. This stops most apps using data when in the background, but you can list specific apps to whitelist and be allowed normal data.

Simple fact is that I only use 3-4GB of data per month when I'm at home. I do use more when I'm traveling, but 3GB/week is more than I'd ever need. Again, everyone's situation is different..