It's only that people have been groping in darkness, unable to really live in that room. If you try to study Buddhism it's not true Buddhism. Koan practice is firmly grounded in zazen, for it is only through entering into the One Mind from which the koans arise from that one ran truly fathom them. The koan cannot be understood by the intellect through study and speculation. One must directly experience the truth out of which these koans arise- not just dwell in theories and ideas.
People ask how to use a koan.
There is no one way to work on a koan. Yet because koan work is an intense form of practice, it is best to work with a teacher. Without a teacher it is very easy to become confused, go astray, or to work oneself into negative mind states or foot oneself that one has attained something. Although a teacher is important, he or she cannot resolve the koan or do the work for the student. Another criticism of koan practice has been that it is goal oriented and thus revolves on the karmic level of gain and loss.