Authority to convert National licences to EASA licences is delegated to the CAA. They decide.
There is a tendency to misinterpret things and whilst training in a non EASA aircraft after a certain date may not be valid for the issue of an EASA licence, conversion of existing licences is a different issue.
Actually, there is no such thing as an EASA PPL. Each State has its own exams; conducts flying training in its own unique way, all of which generically meet the rather vague syllabus requirement, which was provided by AOPA. Finally, each State issues its own licence where the only common part is the four letters EASA.