Wrong, the two initial scans actually form the least accurate version of your face.
The important part that people aren't realizing is that when you record those two first scans, the phone only registers partial information for both scans.
Each scan after that to unlock your phone adds incremental measurements to the full database of measurements of your face.
Now their is a maximum amount of scanned measurements that are kept in this database of facial scans. Whatever that maximum number is, once its reached, you have your most accurate Face ID.
People need to stop assuming, and read the actual information.
Its also important to note that the phone will NEVER have full measurements of all aspects of your face. Apple prevented this so that if the data is removed from your phone, they wont be able to remake your face.