It was a bit untidy BUT it worked at the end of the day.
The MFD timer is neither here or there, it comes up as part of the checklist, so no biggie, though in this instance the 30 seconds is irrelevant.
Bear in mind though that from the 777 flight deck you cannot see the wing at all, let alone the engines, you cannot hear the engines, except maybe at takeoff thrust, the wind is probably blowing the smoke away from you and you are relying on external cues, so from that perspective prob not much different to your 717 Bloggs.
In real terms the difference between a false fire indication and a real fire is, I suspect as I have never had one, difficult to determine, because of the things I listed above, so chuck everyone out down the slides and injure someone and it is a false indication and someone will have a go at you, don't throw them down the slides immediately without confirmation that it is a real fire and someone will have a go at you - so in reality you are between the devil and the deep blue sea.