Yes, I found a pretty legit article actually naming researchers and having better pictures, but it says 30 000 years. Says the paper about this is published in presumably Russian journal 'Doklady Biological Sciences' and there were collaborators in Princeton.
I was wondering that. It seems a more likely hypothesis unless they have some good way of dating them. Maybe carbon date the worm body?
Edit - the paper says
>Some factors prevent the opportunity for nematodes to penetrate into permafrost strata many meters deep from the superposed modern tundra soil. The depth of seasonal thawing in the regions under study is up to 80 cm and was no more than 1.5 m even about 9000 years ago, during the Holocene Thermal Maximum.
and the samples were 30m down so they are arguing the worms couldn't make it though they have only carbon dated the general soil samples and not the worm bodies.