I'm not sure I agree, as I have seen fresh baits left in (heavily fished) areas, and fresh baits eaten in areas where the carp don't think they are being fished for. At Taverham, I spent a lot of time on the water over 10 years, and you could see the fish leave baits in those heavily fished spots, until they had been in the water for a couple of days, at which point they would start clearing them up. The same with the local river, carp would leave sweetcorn on a particular spot until it had started to go grey, they would swim past it, pause, and then only after a couple of days would they come in to eat it. A couple of mates and I spent a fair amount of time there walking the whole stretch, and there is no way, as the carp could swim the whole stretch in the time we walked it (and did almost every day in summer), that we wouldn't see them, so observation was pretty easy. Strangely enough, we didn't see the bream and the tench there, but we knew that they were about as they were often the first fish into particular spots when we fished. The carp would also avoid particular features, one being a gravel bank that rose up from the river bed.
On the occasions I have left hookbaits in the water for a few days, it is often the bigger fish from a water that take it. That is I have spotted larger fish in the spot, and watched them 'control' the area, making smaller fish avoid the spot or area, and then take the hookbait after a couple of days, when my apparent danger is nil (not many anglers leave a bait out for so long without recasting).
I'm sure I am not the only person who has noticed this as Ken Townley wrote about it, and it is a tactic that Albert Romp employed in the past.