You are very welcome -- I am glad you found the discussion useful and enlightening. I find the subject quite interesting.
To have one filter give you 'x' results and another filter give you, for example, x+y or x-z results and finding the results to not be identical is not acceptable to any user.
Such results are "acceptable" to everyone who uses eBay's search feature to buy or sell, apparently, as evidenced by the fact that those users (myself among them) continue to search or list and (in every other way that matters to eBay) accept those results.
You don't know which one of those three results is correct! It thus requires either accepting whatever results you get or continuously experiment with the search criteria to get a more consistent result.
Yes, of course. Most users seem to prefer the former; I much prefer the latter.
In this particular case, though, I suspect the difference has more to do with caching of previous search results than anything else; if you start with a brand new search and try each sort, the results are much more likely to agree, I think, as long as you do not wait too long between performing those searches.
Ultimately eBay is in the business of facilitating transactions, not providing research data. As much as you or I would like to have entirely consistent and logically complete results displayed each time we search, eBay does not claim to provide that.
eBay is interested in providing search results that display items that are likely to be purchased and result in income for eBay. If eBay calculates increased sales volume and profit will result from providing sponsored listings that do not match your search criteria -- or hiding certain results that do match your search criteria -- that is exactly what eBay will do.
