In one sense it doesn't make much difference to the ATCO whether the runway becomes blocked or not. It does, however, make a large difference to the airport authority and the other operators who may face lengthy delays or diversions. For that reason, in the above example, the aerodrome authority may request that ATC pass a message to the pilot asking if he can accept another runway, or even land elsewhere, but that's all it is - a request. Ultimately it is the aircraft commander's choice when and where he lands, and if it's the major airport with full RFF facilities, and a runway and approach that he's familiar with and briefed for, then so be it. As WWW says, the less experienced PPL would feel under much more pressure to accede to such a request at exactly the point when there should be no extra distractions.