The problem with the LAA asking the question is that it represents almost all UK homebuilt owners and would be bound to publish the clarification received, denying its members the choice of deciding for themselves whether a PMD was acceptable or not. A negative reply would close NL to many pilots.
In my view, the requirement for "a valid licence for the aircraft in question issued by a Member State of the European Civil Aviation Conference" cannot be challenged on the basis of some perceived anomaly. It is either valid in the UK, or it isn't, and I would be able to show that my licence is valid in the UK with a PMD.
Admittedly, my view may be influenced by half a lifetime in countries where you would be a fool to ask for clarification of rules or regulations.
I was pleased to see Ed Bellamy wrote
Returning to the PMD requirements, a side effect of the ECAC agreements and some national policies for microlights is that PMD may be permitted, on the basis that the pilot licensing privileges associated with the state of registry are accepted.