Oops! My bad!
Sorry, but this hint is broken. It was generated from irrelevant data. Strictly speaking, it shouldn't have been generated, but it was, so here we are.
The funny thing is that detecting this situation without going through all the rigmarole to build the hints HTML requires us to go through all the rigmarole to build the hints HTML!
So we don't detect this situation when creating hints because doing so involves thousands of expensive operations, which we don't want to invest our time in at the time; so we just deal with "the odd one" here, where we're doing most of the required work anyway... but if this ever becomes more than "the odd one" then we'll have to wear the cost of detecting these irrelevant bloody hints "properly" upstream.
KRC 2019-12-17 The ExcludedCombosMap now goes most of the way towards detecting and rejecting these irrelevant hints, but it's only a partial solution, which isn't a solution, but we'll see this message a lot less often now, which is an improvement, and that's what I'm here for. If you can't solve it then find a way to stop it annoying the crap out of you until you can work out how to solve it. Leave it with me.