I think in this case, the functionality outright broke - that is, this is a bug - due to how their indexing works. The CEO (HN user yegg) talked about it a bit

I think in this case, the functionality outright broke - that is, this is a bug - due to how their indexing works. The CEO (HN user yegg) talked about it a bit in another post - they modified their READMEs to remove mention of some operators because they're malfunctioning. So they still get the benefit of the doubt (as you say, the other choices are just Google) but the real test will be in how they communicate about this going forward and whether they fix it.