These ideas of an attacker and decoy wallets becomes quite complicated for regular people and even for people who are just trying to be practical and spend their bitcoin in various ways having some hot wallets and some cold wallets, but sometimes moving coins from hot wallets to cold wallets and sometimes the other way around, and surely maybe there are ways to mix coins and to make the decoy wallets seem more plausible, but how much time do we want to be spending on the matters of making our decoys more and more plausible.
For example, we go through various efforts to make our decoys plausible, and then if it ends up that the attacker happens to have information about 3 out of 10 of our wallets, and we give him our decoy wallet #6, then at that point s/he has information about 4 out of 10 of our wallets... and we might not even know, until we are being beaten with the $5 wrench, about which wallets s/he has information and which ones not...and if we are being beaten, our thinking might not be as clear as we wished as it would have been under such scenario.
Surely one of the best defenses may well to be attempting to not be telling the whole world about our bitcoin wallets, and so if we are interacting and transacting, there may be ways to get used to rotating through hot wallets and decoy wallets so that there are no real ways for the attacker to really know about the other ones that may or may not exist, and so yeah, how persistent is s/he and is s/he trying to get us to give over bitcoin that we don't have.. but s/he has "good reasons" to believe that we might have more than what we are proclaiming to have during the waterboarding process.