the positive thing first: because relest is auction based landlord will charge maybe higher fees than on a "free market"
but
the negative thing is that the landlord has less options to choose who should occupancy his estate. this might frighten a few landlords
There are rules for this (; ... When someone wins the auction, his or her informations will be send to the landlord. Than they can visit the flat or the house and in this context the landlord can still say no.
I think this is a bit difficult. As I understand it before landlords can maybe say "no", but there is a rating system on the platform.
Let's say there is an tenant who wants to rent a flat of the landlord. He is bidding and wins the auction, which he got shown as ideal, because he has no pets, no kids and is non smoker for example, exactly what the landlord has written what he searchs. Well they meet and the landlord just say no, because he don't "like" the tenant. Well, then he can give a bad rating for this. If there are too many bad ratings, he has to face consequences.
A rating system would be ideal in order to discourage such incidence. This would be beneficial to both tenants and landlords respectively.