Short, because the app barely does anything that touches privacy.
Apart from the licence check described below: nothing. There is no telemetry, no crash reporting and no background service.
The single exception is the Network page. When you press Run Connection Test, it sends pings to 1.1.1.1, a public DNS server run by Cloudflare. It sends nothing else, and nothing about you.
The licence check. Activating sends the code you were given and a one-way fingerprint of your PC to our licence server. After that, the app checks your licence when it starts and every few minutes while it is open, sending your licence number, a renewal secret (stored on your PC, encrypted by Windows) and that fingerprint. The fingerprint cannot be turned back into anything identifying. Nothing about your hardware, games or settings is ever sent.
The licence server records the time and IP address of each activation and of any refused check, to stop people guessing codes and to keep an audit trail.
Everything else. Hardware details, benchmark results, the backups of your original settings and the change log are all written to a folder on your own disk and never sent anywhere:
%LOCALAPPDATA%\ApexTweaks
You can open that folder from the Settings page and read every file in it yourself. The change log is plain text.
Undo your changes in the Restore Centre first, then delete the ApexTweaks folder named above. That is everything the app has ever stored.
Questions about any of this: join our Discord and make a ticket.