When using the default query Updated on the wiki index the page list is as expected (phriction/query/updated/).

However, when you click 'Edit Query' and then 'Execute Query', the form loses its selection of 'Date Updated' in the 'Order' drop-down. This results in a result list ordered by 'Date Created'; the default 'Order'.

This is also the case when you start e.g. from the Advanced Search page (phriction/query/advanced/).