Yep, it was to prevent you from accidentally blowing through your cellular data cap. They no longer prevent the download, just warn you that the app is over 200MB.

The App Store doesn’t allow downloading apps over a certain size unless connected to wifi.

They changed it with iOS 13. It will warn you now, and you can still download over cellular if you want.

https://www.wandera.com/ios-13-app-download-cap-removed/

Note that some of the dropping platforms advice doesn’t really help here, or only helps coincidentally, because the App Store serves you a device-specific app binary.