Perhaps because most fridge compressors have induction motors. These can
pull quite high inrush currents (fom 5*In to 9*In). Add too much extra
resistance and the motor may stall on startup.

Sounds like a reasonable explanation to me - thanks :-)

That said, it wouldn't be dangling off a reel, it'd be the shortest
uncoiled extension / adaptor I could find just to assist access, as
the socket is behind an adjacent kitchen unit - to get the old one out
a few months ago I had to cut the plug off it, as there was no way to
get it out otherwise !

(aka no inductive reactance to worry about)