The regs are badly written, which affects kits. I guess the kits were never anticipated then the lawmakers went to work.
Even a kit whose characteristics are in full compliance with the regs isnt technically legal - the law regards the person fitting it to the bike as the manufacturer, not the builder of the kit, and the manufacturer is responsible for compliance with regulations and, crucially, the fitting the compliance plate/decal as certification.
As a "manufacturer" you must be registered with the vehicle certification agency, or hold DVSA approved certification, in order to prove compliance with regulation 168/2013.
Clearly no individual fitting a kit at home is going to hold such certification, so cannot manufacturer a road legal EPAC.