This is one of those issues where I feel like I should have worked it out faster than I did. Computers are relentlessly logical. If you tell them to ignore something, they're going to ignore it, even if that does confuse your content editors...
There's been a bit of discussion (I might even go as far as to say ranting 😉 ) on the subject of not using "fast query" in your website code recently. I'm a supporter of this idea – but I came across an issue recently that points out why it's not always easy to be confident that you're not making use of it indirectly...
So, for the benefit of Google: