I'm sure we can guarantee, with the feedback we have been given, that the rank 14's in question are likely to be radiant, silvery, azure and dark. Nothing inherently wrong with that but, I think what could be a much nicer reward instead of introducing an account-bound r14 that is likely going to end up being fodder, is to give us some different options.
For instance, we can get rewarded this item or, rank up any enchantment you own (non-weapon/armor enchantment) to r13 and have it account bound. Rank up any runestone you own to rank 13 and make it account bound. Rank up one level of quality (which everyone will likely do the last level) for any armor, weapons or artifacts. That way, folks aren't getting 3-stat rank 14's for virtually nothing. Limiting them to rank 13 is still an effective gate but will be more satisfactory in the end.
edit: Just realized they made it so that it can't even be converted to refinement points.