I have to admit that this is pretty much how I regularly close bugs (company-internal). In my case, I admit that there's a level of intentional sloppiness involved. The decision involves a combination of wanting to reduce my backlog to what's relevant, knowing about circumstances and how they have changed, particularly knowing that the area in question has been highly refactored, such that even if the bug technically still existed, its manifestation would be quite different, and the fact that it's been around so long without having bubbled up to the top earlier. Rarely does all hell break loose just because I have removed a bug from our collective memory by closing it prematurely. Also, often I follow the "much has changed" comment by something like: "feel free to reopen if I got it wrong", and people subscribed to the ticket could then respond (which they rarely do).