Time to nit-pick
The suggestion that a tps trained fast jet pilot would not know how to test a microlight or any other aircraft of which he had no experience is incorrect.
He would know how to. Because that is what his training was all about.
What he would not know is the appropriate regulations and requirements to test against but he would appreciate this and so would dig them out.
Given his zero experience and associated zero currency of the category concerned his training would also make him seek advice from those with appropriate experience and currency. Which would in all probability include some relevant flying. Unless he was a prat and of course there are always some of those in any trade.
To summarise such a tp would not need further training but he would need help. Which is not quite the same thing