I definitely think there's some food for thought in this, though perhaps it comes down to that age-old issue of watercraft.
For a couple of seasons, my most productive chub swim during the winter was a spot where a fairly substantial branch, sticking out some 12 feet in to a far bank swim had caused an immense raft of debris to form. It stayed there for 3 seasons, and whilst you wouldn't really catch much from it during the summer, from October through to the end of the season it was an absolutely banker. Interestingly, it wasn't just under the raft that was productive... the same run behind it for about 12 or 15 yards was seemingly also full of chub. And strangely, it was just as good with the water low and clear as it was with 2 or 3 foot on and the colour of tea.
However, after one particularly high flood, it was almost completely washed away, and seemingly the chub with it. Whilst I can still catch the very occasional fish there now, it's nothing like as productive as when the raft was there.
So do they have winter holding areas? Most certainly "yes".... but in a wider sense, its a question of finding the feature that suits the fish at a given time of year.
Just for reference, the river above is the thames in Oxfordshire.