I agree, it makes little sense to have the MAC filter apply to anything other than wireless.
I'd like to see this as fix to the firmware in a future firmware release.
It would also be useful to be able to set which SSID the mac address can access. A suggestion for those options would be "wireless", "guest wireless", "both wireless", and if you still want to include wired in the restrictions, it could be an additional set of options that would be the same but +wired.
If the filter allowed more addresses in the list, then adding machines that would connect to the AP management interface via wired can be problematic. The list is much smaller than even older Linksys AP devices, and the 1525 is much newer and higher-end than that.