The confirmation is that they were able to observe a decay chain all the way to 258Md. The previous two chains ended in fission (Likely the EC daughter of 262Db, 258Rf). The cross-section for this reaction is very low, worse than the cross-sections in the "Hot Fusion" 48Ca reactions used to find elements 114-118. I think it took them over a year of cumulative beam time just to get 3 atoms. Can't imagine they will go back to this reaction again now that they have the confirmation.
In other news, New presentation from TASCA 12 Workshop at GSI w/addtional decay chains of 117. Alpha decay of 281Rg appears to have finally been observed. ~5-10% alpha branching of this nucleus. Daughter 277Mt has SF lifetime of 10 ms. This is very similar to the small observed alpha branching of 281Ds and the SF lifetime of 277Hs.
There was also a case where the 48Ca beam reacted with the beta decay daughter of 249Bk->249Cf in the target (~25% of the Bk had decayed at this point in the experiment) to produce a 294118 chain.