On their faq they say:
Jumbo Ticket is a secured and certified site which is probably fair. Jumbo Ticket strives for 100% customer satisfaction.
But we can't find any certification link on the site.
You have a point, if they are certified from being provably fair they should have a certification that they are certified because they are now claiming to be certified, the only certification link that is clickable that they are displaying is coming from DMCA, all the others are just icons that are not clickable and those have nothing to do with the claim of being provably fair.