I am often left in front of this situation when hunting for code using advanced search parameters -- they are preventing people from searching efficiently.
Does anyone know what is their motivation behind this?
GitHub's definitely not "protecting" shit; it's just that search is a hard problem, and searching code is a really hard problem, at least at the scale they're at. They're running one of the largest Elasticsearch clusters in the world, and a lot of significant things in code are stop words (or not words at all) in most search databases. Not to mention you need to invalidate entire repo indexes when you force push, etc. It just takes a lot of resources, and like anything, will get better over time.
Now the page is back and I'm not sure what to make of it.
It's a frustrating thankless task to do it of course, but looking for a competitive moat - that will make gitlab and Atlassian quake.