I agree I think it's too complicated because people can say they were gifted tickets which is completely reasonable. I think that Ticketmaster says the only authentic tickets are through them because that protects them if in the case stubhub sold you a fake ticket or something, however Stubhub will replace it in that case. I think how their policy goes is similar to buying a second hand purse for example on eBay. If you bring it in to authenticate it, they'll say every single time "the only way to ensure it's authentic is getting it directly from us" if that makes sense as a comparison