So for example if you google "Food", all the results _will_ contain the string "Food" somewhere in the page (if you don't believe me, try it). It can also match somewhere in the comments or metadata which is useless..
So the feature is still there but it's nowhere as useful as it once was.
I recall a Google engineer who confirmed this once but maybe one of them lurking in the thread can clarify it?
Even if you added quotes to the part number (such as “foo123-x”, google would return results for “foo234-x” or “foo123-y” and bold them as if they had matched. The real part numbers could be 10-20 characters long, so it was more difficult to spot discrepancies.
I learned very quickly not to trust the results even when adding quotes. If I had assumed the quotes had worked, I would have grabbed bad documentation without even realizing it.
edit: It is a pain in the ass though