Trossie, it's a good idea to make sure your example is relevant before you post it - the Okinawa fire was a massive fuel leak onto the engine, not a small hyd leak onto warm brakes, and resulted in an immediate large fire, not some smoke. Saying that fluid leaks lead to fireballs is ridiculous. Stretching the logic, are you going to evacuate because someone sees fluid dripping from the engine pylon during a turnaround? Chances are it's just condensation from cold soaking. Check first, then react accordingly...
I agree that that crew had no option but to evacuate after being so advised by the fire crew to do so - that recommendation put the aircrew in a very narrow and compromised situation, raking away their options. Frankly, I think the fire crew were overzealous and should have informed the captain that there was smoke but no fire and monitored the situation. With the appliances on site, they could have contained any fire that did erupt and then reported that for the captain to then order an evacuation. I think it's wrong that external agents make decisions for the pilots rather than just give them the information that is needed in what was an urgent, not emergency situation. Had this been a taller aircraft, more serious injuries would have occurred, all unnecessarily.