You'd need to read it at least 20+ times before it starts to stick in your head.
Psychological pressure is enough for that, I remember that when there are remain five minutes to finish the exam, I forget all information.
It sounds funny, but that doesn't have to do with the pressure, it's called a the doorway effect, that there's every tendency a person will forget half of everything they've read once they pass through the door of an examination hall, compared to when they're in their reading room. It happens to almost every student, and humans will need to relax and think to remember what is been stored in the brain.
I guess that only happens when you study for it once. If you are indulging in the information continuously, there is a very low chance that you'll forget most of it. Not much of a problem for seed phrases as you should be etching those onto your mind before you start using them to store serious money.
A USB flash drive is not the worst method of a backup for your seed phrase, but i will still choose paper over it. USB flash drives have a lifespan, and even if it is not too short, it can become corrupted earlier on and you would lose data stored in it, which you can only recover most times with the help of a third party service, and that is not recommended because the data stored there is your seed phrase and it can be stolen by this third party.
All devices have the possibility of breaking down and that's a given, but it also depends on maintenance and how durable the device or USB flash drive is.
I found a few recommended USB Flash Drives that seem to have good initial security as well as resistance from extreme conditions.
It's not so much about the security as it is about the reliability of the device (it is easy to physically destroy it for instance).