@Ianosh 
I noticed that the MAC is actually different. So it seems it's 2.4 and 5 Ghz. That's very inconvenient that one have to connect to both bands in order to turn the parental control for all devices... Is there a solution for that? Maybe a white list insteead?

@Ianosh 

With the Note 6, I would turn off random MAC address: https://www.techrepublic.com/article/how-to-enable-a-randomized-mac-address-in-android-10/

For the RE200, any device that connects through it will have a different MAC, compared to connecting directly to the router. So if the Note 6 is doing that, reference both MAC addresses. 

For the RE200 itself, was it ever configured as an access point? Also, look behind the device it will show the related MAC addresses, which does it match?

@Tony 
I, as a customer, can say for certain now that the parental control is almost useless. I am a programmer for 30 years, and I can with authority say that it seems no one tested this functionality in real life with dozens devices, which is a very probable case when someone buys an AX3000.