I used down back in the 1970s and 80s.
The problem with down is it is very slow and hard to dry out.
I would never on good conscience recommend a down baq for emergency or expedition use.
I am willing to accept the trade offs and benefits of good synthetic bags.

(But I still love my down parka for -40 weather)

"He would rather be in a blizzard at subzero temps than be caught out in the wet, just above freezing."

Heed the man.
And tell him to stay out of the UK.
Because those are normal winter conditions for us.