In my airline who flys close to 2000 sectors a day on the A320 series it is SOP for both pilots to hold the side stick. If a side stick fault developed or a takeover due, poor technique or incapacitation then you an immediately ready to take over. It is routine for the captain to take over during a poorly executed landing, for a number of reasons. I have had to do this several times over the years, including a long flare on short rwy. We must touch down in the touchdown zone and in my airline it’s SOP that the captain flys the baulked landing. I have never experienced or heard of any detrimental effects of duel input, the warning is very useful as it A, reminds the take over pilot to press the red button and B, reminds the other pilot to let go of their stick! Of course the pilot taking over needs to also announce I have control. It’s not a big deal and like I said is routine.