Seems to me that the creator of that site is shortsighted in how he or she confirms who the assassin is. Namely, that the assassin has to be able to specify the date of death prior to the death.
in other words this could be seen as an office pool (with no actual buy-in): guess when controversial government official X is assassinated!
Frankly, Sanjuro is either a nutcase, or a honeypot. In either case, it would be best to avoid him.
so you think that paying money (under real or false pretenses) to have someone killed is something to be avoided? your wisdom is inspiring.