Ending soonest (theoretically) includes all BIN items in order, so if they have an hour to go before they tick over, they should be near the top, but I can almost guarantee you (from experience) that it doesn't matter what search order you use, you still don't see all available listings. 

So many times I've entered a search (my default search order is ending soonest), then refined it slightly so that I get less results, then items that should have been included in the first results will suddenly appear.

As an example, say I search 'red beads', there will be a whole bunch on the first page ending in the next half hour or so, but heaps of them will be ones for Pandora style charm bracelets, so if I refine the search by adding -European, all it should do is remove most of those from the results, but when I do, more red bead listings that are ending sooner than previous first page results, so should have been in the first set of results, will suddenly appear, clearly indicating that relevant results were omitted.