See e.g. https://en.wikipedia.org/w/api.php?action=help&modules=query%2Bwatchlistraw. Description of wrdir states that
In which direction to enumerate:
newer
List oldest first. Note: wrstart has to be before wrend.
older
List newest first (default). Note: wrstart has to be later than wrend.
One of the following values: ascending, descending
Default: ascendingValues newer/older are not applicable here (apparently copied over from list=watchlist or other similar action). Also there are no wrstart and wrend parameters