Google synonyms a bit too far off

For quite some time, Google has been using synonyms and variants (e.g. singular versus plural) in search results to help the user.

But recently, it's been going a bit too far in its "inferences" about what constitutes a synonym.

The double-quotes operator used to mean exact match, but either Google Scholar ignores it completely, or Google is simply ignoring the user:

I looked for flexibility, but is only matches results with angioplasty, as if it were a synonym. I put "flexibility" between quotes for an exact match, but it didn't work.

If Google Scholar couldn't find anything with "flexibility", it should at least say so, as it usually does in Google Search: no matches found for term X, searching with Y instead.

This is completely unintuitive and provides a bad user experience. Let's hope Google fixes this soon.