It doesn't quote IAS, it just says "cruising speed".
Even money that's TAS at altitude. 147kn TAS at 10,000ft is about 126kn CAS - or about the same as you'll get out of a CT. (And a nominal 75% power at that altitude will be about full throttle.)
It's a common piece of fiction regularly seen in aircraft sales brochures - it's just that the UK microlight industry is unusually honest (usually!)
G