Mode confusion between TACC and AP/FSD is a DESIGN problem. It's 100% on Tesla. If anyone puts it in TACC but thought they got AP, that shows Tesla did not do enough UI testing. You need to account for the distracted driver, kids in back screaming, on the speakerphone with the spouse, dog barking.
Different actions should engage different modes, not using the same stalk and doing single and double taps. I miss the second tap all the time (actually, I do the second tap but mess it up, too quick after the first, or an incomplete tap, not all the way down). Usually catch it when I check the screen to confirm, but sometimes just notice the car drifting. Needs a totally different input method for the different modes.
But I totally believe AP could drive into a tree. Mine tries to all the time at a fork by my house.