Question : If the PF was consciously following the prescribed procedure for UAS - then why did he not, at any point, tell his colleagues he was doing so?
In fact one of the overriding perceptions of the sequence as a whole was that there was never at any point a co-ordinated effort to troubleshoot and apply procedure. When the PNF stated "you're going up", the PF did not respond with "I'm following UAS procedure" - which would in all likelihood have unlocked the mystery for the PNF and allowed for corrective action.
As a non-pilot I am constantly and sympathetically aware that I cannot feel the visceral hold to the idea that there must have been some reasonable explanation for the actions of the PF. I accept that there's a possibility that he was applying a half-remembered UAS procedure, but for the life of me I cannot understand why he would not say he was doing so.