Large increase in DTTG size on iPhone

I have upgraded from DTTG 2 to 3 and changed sync from iCloud(legacy) to iCloud (Cloudkit).
Its all gone seamlessly. However, I’ve just checked the app size in iPhone storage and my iPad storage and found the app size on my iPhone is now 7.5GB whilst on my iPad its 3.5GB.
Prior to the changes I think the app size was about 3.5GB on both my iPhone and iPad.
I have deleted DTTG 2 on both platforms after the upgrade has been made.
Any suggestions why? I thought I’d delete the iPhone app (with the 7,5GB) and reinstall. But its all working fine so really don’t want to upset anything!

Did you clean the iCloud (Legacy) sync store? Otherwise it might still require space.

Yes I did clean the iCloud sync store on the Mac version. Presumably that would delete it from the iOS apps? The iPad version is no problem.