I don’t think this is an ADHD thing. Brains delude us into false senses of control in all kinds of ways. For example, withdrawal reflexes like jerking a hand back from a too-hot surface are carried out by neurons in the spinal cord before the too-hot signal has even traveled to the brain - but we feel as if that jerk was a conscious decision. Recognizing that fake sense of control is an illusion is helpful in figuring out what few levers we do have and learning to use them.
https://en.wikipedia.org/wiki/Reflex_arc
The brain will receive the input while the reflex is being carried out and the analysis of the signal takes place after the reflex action.
For me, it happens especially with activities I do over and over again. Washing my hair, while rinsing I will forget if it’s shampoo or conditioner I am rinsing out, have to try to deduce it. Morning stretches I have to do in the same order, because I can remember the order to recognize where I am and do the next thing, but I have no memory of what I just did.
Keeping track of one-time sequences is also a problem, but at least in that circumstance I am more likely to have written material I am referring to anyway.