France has a joint aikido organization for the purpose of issuing dan grades in accordance with the government rules. Maybe the "jury" is that big, because they need to have representatives from several of the aikido federations cooperating in this grading organization.
In Japanese kendo and iaido examinations, there are usually several people in the "jury" - the more, the higher the grades tested.
In aikido, there are many cases where one shihan alone is the judge. That is not at all common in other budo.
In Sweden, we normally have three persons judging dan examinations. I have the impression that this is often the case also in other countries.