In Derbyshire/Staffs at the moment we have anglers complaining that the grayling are still feeding, then fish the duo to make sure they don't have a chance

. of peace. Surely any decent angler would fish dries to at least give the lady's some chance of avoiding capture out of season, if only for a few weeks until they fade away a little.
I have no problem with fishing the duo or bung but I suppose they are similar as you say, but the duo on the river in trout season is simply not necessary in my opinion.
However fishing stocked still waters is fantastic sport with buzzers under the bung, and I always look forward to early season buzzer fishing in this way.
Mick