I suppose the key is "Supersonic". The Buffs obviously didn't fly Mach 1
So they want to beat the 1957 record by more than half.
It's not a round-the-world flight. They are flying from Engels AFB over the Arctic Ocean, skirting Alaska, flying around Japan and then over Siberia back to Engels. And the video mentioned that only 10 minutes are spent in supersonic cruise.
Sure, it maybe a record for Tu-160, but not a world record.