I am not sure the information you have is entirety correct. Let’s review some information about acetylcoholine and its role in memory and learning from a Neuro textbook.
“Acetylcholine enhances the activity of various cortical neurons, causing suppression of membrane potassium currents and thereby causing depolarization and suppression of adaptation. This could certainly enhance memory function. However, many studies show that, along with suppressing adaptation of neurons, acetylcholine also suppresses synaptic transmission. If acetylcholine is important for new learning, why would it suppress synaptic transmission? This paradoxical combination of effects was clarified when it was found that the suppression of synaptic transmission is selective for intrinsic synapses (connections between cortical neurons), but not for afferent synapses (connections arising from outside the cortex).”
Basically, they figured out that by shutting down synaptic transmission for intrinsic synapses the brain would not be interfered with by previously stored information while it was trying to learn new information and patterns. Acetylcholine’s role in suppressing synaptic transmissions works to create a brain state that is the most condusive to learning.
Phosphatidyl Choline is the most abundant phospholipid in cells. These phospholipids provide the main structure of cell membranes and play a crucial role in inter and intra-cellular communication. Most choline in the body is stored as phosphatidyl choline and can be used to manufacture acetylcholine. Upper limits of phosphatidly choline supplementation are not known and appear to play no part in shutting down of the learning process. More likely, phosphatidyl choline contributes to the balance of activation and suppression of synaptic transmission needed for learning by assuring adequate avialablity of acetylcholine.