Regression (since 2.1.0): very slow scanning when dealing with identical files

What happened?

Creating a new issue since #10777 was closed, I cannot reopen it, my requests to reopen it (here and here) were ignored, and the regression was not fixed.

I can provide new support bundles when the final release of 2.1.4 with https://github.com/syncthing/syncthing/pull/10849 is out.

Syncthing version

v2.1.3

Platform & operating system

Arch Linux x86_64

Browser version

No response

Relevant log output