He knew techniques were the result of many generations' effort of genius spirit masters. Most techniques came from old times and were taught to the new generations by the direct teaching of masters.
However, this wasn't the only source for this. After the many losses humanity suffered, they learnt that entrusting techniques only to the strong and experienced spirit masters was a risky move.
Once the spirit master died, then all the knowledge he had would be lost with him. So, the trend of storing the techniques in records became the basic rule in this world, like it was in the outside world.
And that opened the door for such a bad situation he just accidentally discovered.
William didn't know that his thoughts aligned with the headmaster who sneakily spied on what he did with John. William also suspected that someone must have changed the original records with other weak and faulty versions.
That meant danger in William's eyes. If this was true, then humans were doomed!