@e-techniker Indeed, this ends up being a frustrating limitation of the EasyMesh system.
To be fair, I can see where they're coming from - it seems quite obvious that TP-Link originally intended EasyMesh primarily for use in Wi-Fi mesh networks (where the backhaul between nodes is via Wi-Fi) first and foremost, and then only added the Ethernet Backhaul and AP mode features as an additional capability down the line. Presumably, that's why EasyMesh continues to maintain the wireless backhaul channel in the background and does not allow you to switch it off, even when using Ethernet Backhaul for all nodes in the mesh.
It is pretty frustrating for me - and, presumably, the not inconsiderable number of users out there who want to use EasyMesh not for its actual Mesh features, but rather the seamless roaming it provides when running a mesh exclusively composed of Access Points: that is the unique selling propoposition of EasyMesh, in my opinion, when compared to other vendors who aren't able to provide this feature.
Is there a specific technical reason why it's not possible to have this seamless roaming experience using EasyMesh AP mode with ethernet backhaul, but where each node uses a different Wi-Fi channel? Because that would be the dream - seamless roaming, but without the interference caused by all of the Access Points trying to use the same 20MHz channel.