Thanks for the ping. This is a very interesting and important discovery. It leaves no doubt that these specimens contain extraterrestrial fragments.
The authors are trying to tie together the 13KYA and 35KYA evidence, but that is speculation.
The Siberian bison survived the impact; therefore, the date of that skull establishes the date of one impact. The article doesn’t have the date of the Siberian bison skull, but it seems to be one of the 35KYA specimens. If so, there is evidence for two impacts, one at 35KYA and another at 13KYA.