The reasoning you give to a bounty is not about why you gave the bounty; it is there to guide the visitors to your question what you are looking for with your bounty, this can be clearly seen in bold:
Authoritative reference needed
Looking for an answer drawing from credible and/or official sources.
Canonical answer required
The question is widely applicable to a large audience. A detailed canonical answer is required to address all the concerns.
Current answers are outdated
The current answer(s) are out-of-date and require revision given recent changes.
This question has not received enough attention.
The current answers do not contain enough detail.
Reward existing answer
One or more of the answers is exemplary and worthy of an additional bounty.
not yet received an answer which solves the problem falls under Draw attention; because you basically haven't gotten attention yet from an expert that does know a solution to your problem. So, by giving a bounty you state that you are looking for more attention with reputation in return...