I'm a bit lost, how is this different to, for example, a one year rental on an apartment? My contract says 1 month's notice (before the end of any month) is all that's needed. Why are some 3 months? Am I misunderstanding some difference?
You have a contract for a fixed period of time 6-12 months with one month termination for both parties, at the end of the contract if you decide to extend the contract indefinite your new contract will automatically require a three month notice period. In your case Inwro you ask for a further 6-12 month contract and go through the whole procedure of signing it, many landlords do not want the agency to redraft a new contract as there are normally fees/commissions to pay by the lessor, they also realize by law they are locking the lessee in to a long term contract by not have a new fixed contract.