@BDuplan,

I will have to look into this further but I have a pretty strong hunch that the behavior is being caused by the relaying/proxing of traffic through the ubiquity CPE. I would try looking around their support resources or contacting their team. The two MACs are likely from it connecting to the different network interfaces, and they may have an option to disable this or hints on what to do in your case.

Does the behavior also exist if you create a parental control for only one device at a time?

I would recommend checking that the MAC address that does not match the real laptop address is not just the address of the CPE or is using a part of the CPE's MAC address. If so, it is likely to use a system closer to a Range Extender to network devices. Also, make sure that you do not have AP isolation enabled on the network/AP.

  @BDuplan,

In case it helps/relates: I believe that for our REs, this behavior of spoofing the MAC is referred to as Proxy Mode or 3-Way Addressing Mode - and is, unfortunately, a setting that is reliant on hardware and affects all devices connected through the RE. Without having the Router see the specific MAC address or a MAC address that points directly to that device, it will not be able to block. 

While it may be a bit longer of a shot, you may be able to configure something similar through static routes.