iCloud Backup data discrepancy with disabled Share iPhone Analytics

In the less than 24-hours since my last iCloud Backup my iCloud Backup for my only iOS device has gone from 53.66 GB (recorded during Backup process) to 55.35 GB (during Backup process) for a + 1.69 GB data increase.

That data increase during the Backup process is only for 16 additional screenshot images (0.007926 GB), and one .pdf document (0.0031 GB), for a net value of 0.011026 GB.

During the iCloud Backup process, my Photo Library lists 58.17 GB of data, with Files listing 42.14 GB of data being backed-up.

Once the iCloud Backup process has been completed, the Photo Library lists 34.6 GB (–23.57 GB), with Files being 21.82 GB (–20.32 GB) of data backed-up.

Ie. once the iCloud Backup process has been completed, some sort of correction is applied to subtract the respective data amounts from those stated during the iCloud Backup Process.

Where is the additional data of 1.679 GB originating from if not from my Data Analytics which has been disabled so as to NOT share any Data Analytics types (iPhone, iCloud, Improve Siri & Dictation, Improve Assistive Voice Features, Improve AR Location Accuracy)?

Please do not reply with any statement that states (or is similar to a previous question to not worry about the data discrepancy/differential and correction) as I am writing to be informed as to:

1. Exactly what data is being collected (previously when I have turned on "Access iCloud on the Web" and submitted a "Data and privacy" report, said report only states that "No data available" for "Other Data").

2. Exactly what data is not permanently anonymised (requiring that the anonymised data can not be used on a granular level for re-identification/de-anonymised purposes) when collected, and the legal justification of that data collection that is not permanently anonymised.

[Re-Titled by Moderator]