The explanation for what the global StackExchange "bounty reasons" are goes back six years to this StackOverflow blog by Jeff Atwood, "Bounty Reasons and Post Notices".
Looking only at the Question above on Meta, you write:
I specified "canonical answer needed"... because if the question can be answered non-negatively, then my team needs to be able to say that the desired nearest-neighbor relation has been defined by someone whose background qualifies his or her answer as "authoritative".
Based on that phrasing I would likely have chosen Authoritative reference needed ("Looking for an answer drawing from credible and/or official sources."), rather than Canonical answer required ("The question is widely applicable to a large audience. A detailed canonical answer is required to address all the concerns.").
As a practical matter these phrases both make clear that you want to reward new Answers, rather than to Reward existing answer, but since there are no existing answers, that point is implicitly clear. When no answers are yet given, Draw attention seems especially apt.
Looking beyond the "bounty reason", into the post on Main, the clarification of "internally consistent" in terms of exact counts of neighbor-distances is welcome. An interested Reader would still have some work to do to reconstruct the rationale for those counts, but it would be motivated by the linked previous Question.
Generally I'd recommend further clarification, esp. of the notion of "nearest neighbor" as it connects to the Hamming code analogy. The more accessible the Question becomes, the more likely a Reader will be able to respond quickly and cogently.