For those who have read Swift, I suspect this 'do you clean the brass before or after decapping' could turn into a 'big-endian little-endian' argument which is something I wish to avoid.

So long as the flash holes are checked as clear I don't see a problem. Personally I would rather run clean brass through a die than dirty; the positive thing about Tac's raising the issue is one of reminding any readers to check the brass thoroughly once cleaned INCLUDING the flash hole and primer pocket MOST ESPECIALLY CAREFULLY if using steel polishing media in a wet tumbler.