No surprise....
Gentlemen:
This is the 'boiler plate' axiom for anti-ice use. It's Boeing's policy...but Airbus', as well. It's a certification issue (JAA/FAA) and the engine manufacturer's policy.
There have been cases of flameouts at high altitudes, especially (but not exclusively) during descents.... idle thrust, high altitude, cold temps (colder than -40c), in the area of thunderstorms (convective activity)...where the Einsteins in the cockpit chose not to follow SOP.
DUH!!!!
"None" quoted things correctly.....
Fly safe,
PantLoad