That's not true, "there is a chance" that other products will detect it too.
No doubt that there is a chance.
But, as I said, these KL simulators are written to be absolutely and obviously detected by the respective vendors.
This doesn't mean that an AV can not detect them via signatures or keystrokes detection.
It can, but these simulators are not the best way to test the AVs in this context.
If real keylogger malware uses GetAsyncKeyState, a common function, then it returns as the key is pressed or not at the time of the call. It is detected because the malware is making a system API call, and it is easily detected by an AV as the hook on Windows messages also.
But if a real keylogger uses hypervisor or kernel-space (virtual machine or driver) for example, it can really hide itself and you can really test a AV in the correct way, not with a simple simulator's test.