That's completely untrue. I wish the Disney call center operators would stop spreading misinformation.
The Port Orleans Riverside room assignment team would
prefer to place guests with dogs in building 24 if they can, however should a guest in ANY booking category turn up with a pet then they will need to be given a room in the category that they have booked. There are other locations that have been assigned as backup dog-friendly areas for guests with Preferred Location, River View, or Royal Room bookings (none of which can be accommodated in building 24) but even those cannot be 100% guaranteed.
As far as I've been able to ascertain, suggesting that paying more money will in any way guarantee you a room in which no dog has ever been present is a complete lie.