This query has results ordered by (ns_num, title) in descending order, which is hardly an appropriate default ordering (e.g., pages from the main namespace come last).
The documentation for list=alldeletedrevisions says:
In which direction to enumerate:
List oldest first. Note: adrstart has to be before adrend.
List newest first (default). Note: adrstart has to be later than adrend.
That is the timestamp-based ordering, but in practice that happens if and only if the adruser parameter is supplied -- if it is not supplied, the ordering is not timestamp-based but title-based.