It's not strange, because you are finally informed - in writing. This has only been the case for a short time (2-3 years?). Otherwise, you can simply dispute the thing later... We also got a letter back then that we had to sign, explicitly stating that the agent received a commission from both parties. He, the agent, earned his money though, because he really took care of everything until the notarized contract was concluded, negotiated with the seller (successfully, so we practically had no commission plus 1000 extra). For the first time, I genuinely wished him his commission...