So what's canon here?

[griffon8]

... even suggesting that Kenji just use his own peephole.

So what's the deal here? Are peepholes canon or not?

Kenji's door in the dorms is also described as "sounding like it has 10 locks on it". I wouldn't use Kenji as any sort of example of what is normal... even for an unusual school.

I always figured that was just Kenji unlocking and locking the same lock over and over again. Testing it to make sure the lock was working. That would explain how he's able to get it open so quickly from the outside.

But it would also work if he couldn't lock any of the extra locks on his way out if there weren't any extra keyholes on the hallway side of the door.