I often notice that when I use the SE cross-site search engine (which is powered by Google), I get just a small subset of the results obtained by searching Google with the operator: site:stackexchange.com
.
In many cases the additional results found by Google are meaningful appearances of the search term, which are not duplicates of the appearances found by the SE engine.
Here are a few examples for the number of search results obtained by each method, at the time of writing of this question:
╔══════════════════╦════╦════════╗ ║ Search term ║ SE ║ Google ║ ╠══════════════════╬════╬════════╣ ║ football manager ║ 6 ║ 1120 ║ ║ roomba ║ 3 ║ 1490 ║ ║ papercut ║ 8 ║ 180 ║ ║ treehouse ║ 2 ║ 552 ║ ╚══════════════════╩════╩════════╝
Is there a good reason for this discrepancy?
Is this a bug?