The first part sounds like a pretty terrible UI bug - it should be showing as out of stock everywhere :thinking: maybe the search results don't cross-check your selected store location but the detail page for an item does. (not excusing it just thinking where the issue could be)
A couple of reasons to show items they can't sell you right now in the search results...
1. The best reason I can think of is if you click into it and it isn't available then they could show "similar" items and cross-sell you on those - and maybe actually help you find a good alternative.
2. If you are searching for a specific item then the result should show you that item regardless of availability or you'd just keep looking for it and be confused about it never showing up in their results.
3. Maybe SEO? More listings - even out of stock listings -> more SEO juice
A couple of reasons to show items they can't sell you right now in the search results...
1. The best reason I can think of is if you click into it and it isn't available then they could show "similar" items and cross-sell you on those - and maybe actually help you find a good alternative.
2. If you are searching for a specific item then the result should show you that item regardless of availability or you'd just keep looking for it and be confused about it never showing up in their results.
3. Maybe SEO? More listings - even out of stock listings -> more SEO juice