Using --append-verify sometimes causes spurious "failed verification -- update retained (will try again)." warnings

[TheCompGeek]

Version: 3.3.0 (Protocol version 31)
OS: Debian Testing
Platform: x86_64

Description: Invoking rsync as follows:
rsync -aEAXHi --progress --append-verify /path/to/source/dir/ /path/to/dest/dir/
sometimes causes spurious " failed verification -- update retained (will try again)." warning messages. I've attached a dataset pack containing two datasets. If the second one is copied over the first with the above command syntax, this should cause rsync to emit warning messages. Manually verifying the checksums of the warned files returns matching checksums from the source file on the second dataset and the destination file in the test directory. Additionally, omitting --append-verify results in these warnings not being emitted.

WARNING: The test dataset archive is extremely large (86GB). Please ensure that you have at least 200GB of free space to decompress the archive and reproduce the issue.

Test dataset archive link: https://drive.proton.me/urls/B1RXK0QRC0#dmtMbm9WnpAM

Steps to reproduce:

1. Extract the dataset pack, which contains three folders; two containing the two datasets and the third containing an empty folder. Use --use-compress-program=lbzip2 for multithreaded Bzip2 decompression.
2. Copy the first dataset into the third folder using the above command syntax.
3. Copy the second dataset over the first dataset using the above command syntax.

Expected behavior: rsync does not emit warning messages, as the contents of the source files in the second dataset and the destination files in the test folder should match, as verified with sha256sum.
Observed behavior: rsync emits spurious " failed verification -- update retained (will try again)." warning messages despite the files' contents being identical, as verified with sha256sum.

Workaround: Downgrade rsync to version 3.2.3 (Issue not present in that version), or omit --append-verify from invocation command (which reduces data integrity verification and is not highly desirable in my use case as a result)

Other Versions:

• 3.2.3-4+deb11u1 (as packaged in Debian Bullseye) - Not affected
• 3.2.7-1 (as packaged in Debian Bookworm) - Affected
• 3.2.7-1~bpo11+1 (as packaged in Debian Bullseye Backports) - Affected