If I recall correctly, the requirement for microlight differences training for SEP holders was introduced as a result of an AAIB recommendation following a number of accidents.
The requirement to complete differences training for transferring control types for people who hold the privileges to act as PIC on microlights was also introduced as a result of an accident and resulting AAIB recommendation.
I think you recall quite correctly that the requirement for Differences Training when transferring between control types was introduced as a result of AAIB recommendations after a number of accidents.
I think that the drafting of this requirement, and it's subsequent re-writing when EASA Part.FCL was introduced, produced the wording we have today which suggests that there may be a requirement for Differences Training when flying any kind of Microlight for the first time.
I would suggest that, if this had been the original intention, it would have been included in the items requiring Differences Training listed in CAP804.
MJ
