Highly doubt he will ever do this because the money isn't actually guaranteed, regardless of his claim that it is. It is the amount that he plans to pay out IF the gate proceeds turn out as he hopes and IF his food and drink sales are what he expects them to be and IF everything else falls into place as he hopes and plans etc. A perfect example is the year the blizzard or earthquake or whatever it was (forgot now) kept the spectator attendance low. He didn't didn't pay out all of the advertised added money and his excuse was the blizzard kept spectator attendance low and he didn't make enough gate money to be able to pay all the added money that he advertised and promised. Essentially the "guaranteed" added money is a meaningless claim as it is always dependent on something else and is not guaranteed at all.
I'm sure I will be corrected if I have some facts wrong but I'm pretty sure the gist of my point is correct, the money isn't truly guaranteed at all. The added money is always dependent on other things properly falling into place even though he doesn't tell you that part. If money is truly guaranteed, that means that you have it set aside ahead of time, and it isn't in any way dependent on anything else needing to happen or not happen. It will be paid out come hell or high water. But most promoter's definition of guaranteed money is "the amount I hope to be able to pay out if all goes as I hope it will". There is nothing guaranteed about that.
Which brings up another point. In my opinion, for any event with a sizable added money amount being claimed as "guaranteed", a promoter should always escrow that added money in advance. If they are not willing to do that it is almost certainly because they either don't really have the money at all and are hoping to get it through gate sales etc (in which case it was never really guaranteed money at all), or they do have the money but don't intend to pay it all out if they don't do as well with the event as they hope to (in which case it was never really guaranteed money at all). If the money is truly guaranteed there is zero reason not to escrow it in advance. If you have it, and intend to pay it out, then you can escrow it.