I can say with confidence that the advice your friend was given is correct or at least in Aus. The rims that runflat tyres are fitted to are reinforced in design to accommodate the increased stresses inflicted by the lack of yeild in the side wall of run flat tyres which is how they remain relatively intact in the event of pressure loss. In Aus it is illegal to fit runflat tyres to standard rims. ( I have runflat tyres on my E53 )