I think apples are being called oranges here.

Pegasusnnnn seems to be speaking of a OneWorld Expolorer ticket (AONEW3, etc.), which you purchase for real money (rather than accrued miles). Itineraries on these tickets can indeed be changed after they're ticketed, once for free before the trip starts and for $75 either for subsequent changes or after travel starts.

Mcrt, sunil, and everyone else appear to be speaking of an "award ticket," which I interpret as a ticket for which you pay miles from a 1W carrier. I don't know of any specific RTW award, though of course there's the mileage-based 1W awards -- the number of miles you need to pay depends on distance traveled and class of service.

It would help a great deal if everyone were discussing the rules for the same program.