I think Hamilton was being warned about it before RB enquired but in any case I don’t see what the problem is.
Anyone could have done it and then everyone was told they could not. There wasn’t a point in the race where Hamilton was getting an advantage that was denied to others. Drivers seek to squeeze out every last 1/100th they can until told otherwise. They aren’t known for being shy and retiring with such edge decisions.
Plus, you can’t just say that he did it for x laps and gained y each time so actually gained (xy) seconds. Races don’t work like that.
There is also a case to be made that running wide may not have been the best strategy for retaining tyre life (which was as much of a part of the Merc strategy as pumping out 10/10ths laps.)