Suppose you have multiple PTR records for a given address. Then this happens:
1) A request is made for PTR records for the address, by something trying to verify one of the hostnames.
2) The server treats the set of PTR records in round-robin, "load sharing" the results. In effect, it reorders the records in an essentially random permutation, and reports them all.
3) The requester sees a stack of records, but only reads the first one. The rest are assumed to be supporting records (NS records, etc.). Thus the result is a randomly-chosen record from the set of PTR records.
There is little chance that the resulting name matches the name that was started with.
