I had a similar event happen to me in 1121 Jet Commander on an engine replacement test flight back in the late 1970s. After takeoff the number 1 engine thrust lever would not move, staying at takeoff power. Finally after a lot of radio conversations between us, the overhaul facility and General Electric I was given permission to shut the engine down with the fire handle.
The reason for hesitating to shut an engine down running a full power with the fire handle is that such action can cause a lot of damage to the engine. Which it did, the hydraulic pump cavitated and contaminated the aircraft's hydraulic system and the oil pump suffered similar damage.
So, back to the hotel for another few days.
However, in the case of the Air France 74 I am curious as to why the crew did not use the fire handle to shut the engine down when it ran away to full power. One engine being damaged is a lot cheaper than the whole aircraft being written off.