There are deviations in the detection results of each system. Because the algorithm of each detection system is different, the database of each detection system is also different.
Relatively speaking, HowNet's database is the most complete. However, it cannot be asserted that the system detection of HowNet is the most standard.
The definition of this standard is vague at first, just like college students' thesis detection, the duplicate checking system of the school's thesis may be different, but 80% of colleges and universities use HowNet, and the rest use VIP, pp or others.
The HowNet exam used in our school, you found it yourself with pp in advance, but HowNet failed. You said that the pp system is not accurate, and the knowledge network is accurate. The other one was tested with pp at school. You tested it with HowNet in advance and passed. Later, the school failed the pp test. At this time, you said that pp was accurate, but HowNet system was not.
The conclusion is: you can test with whatever system the school uses. This is the most accurate!