Is the contents of the familiarisation training specified anywhere in FCL?
No. It could be reading the Flight Manual
By "having it", I suppose that means as a type in the logbook? I.E.
Cessna 182 = SEP (land) with variable pitch propellers
No need for the type; VP props, or any other difference is valid on any SEP, no expiry. For MEP it is type related and valid for 2 years.