Is Photos Duplicate Cleaner.app malware?

https://www.systweak.com/systweak-antimalware reports that it is, itself, an Anti-Malware program!

Most alleged anti-malware things are in fact malware and can only reasonably be classified as such.

Is this malware and if so, should I report it to Apple as one generally assumes programs in the AppStore are tested as safe?

Submissions to the Mac App Store need to meet certain requirements. It is absolutely possible for an app to meet them, yet be considered "potentially unwanted" to someone else.