Oloren's creation of a hole through the door reveal that the door is attached to a series of chains, chains that are also held together by the arcane lock. Uneducated in trapcrafting as he is, Oloren may guess that it's carefully rigged to release the trap door if the arcane lock were dispelled or the door moved or it's weight changed, via destruction, or some of the chains severed. However some chains are still moving in the background as he looks through the hole.