When an engine is first constructed or rebuilt correctly the bores are honed to give a matt finish rather like a fine nail file. This is done on purpose because the piston rings, which seal the piston against the walls of the bore, have to wear in together with the bores to give as good a fit as possible. It was not possible then, 20 years ago, to machine the bores and rings to such an accurate fit. It may be now as over the last 20 years improvements have been made. The glaze is a result of the engine being run for the first few thousand miles, when the rings and bore wear and polish themselves together, and is very hard and it's achievement is on purpose. It's a bit like polishing steel with metal polish. Metal is removed but the surface is shiny and in the case of the rings and bores the surface becomes very hard due to the properties of the metals. If new rings are fitted to a glazed bore they will not bed in so will always be a less than perfect fit.
When I took the head off my 1hd-ft I could still see traces of the original honing marks giving testament to the very long life of these engines. There was hard glaze there though where the top of the of the original honing had been removed by ring wearing the bores. This engine had done about 140,000 miles.
Shayne I think glazed bores are only a problem when new rings are fitted without first removing the glaze. It's meant to be there after the engine has been run after new or rebuilt properly.