No. The Mirror has it’s own separate sourcing in Britain.
“The reports were backed up by a UK special forces source back in the UK who spoke to the Daily Mirror over the weekend.”
https://www.mirror.co.uk/news/world-news/sas-chiefs-refuse-us-request-24814423
LOL, look at those words, there is a reason the story never made it and stayed in its little unsourced speculation low end places.
You original source said “I understand that”
“The Mirror has learned”
“A controversial American media report said”
“The reports were backed up by a (unnamed, unranked, don’t know if he or she is in any military unit, or anything about the supposed person) UK special forces source”