A & C - trust me. Skydrol WILL burn. I've seen first hand the resultant fire caused by hydraulic fluid leaking onto hot brakes. I should know I attended the award presentation today to the colleague of mine who spotted the smoke on CCTV and crashed the Fire Crews.
What followed the white smoke was an approximately 12 foot fireball when it ignited followed by a sustained fire until the fire crews could mobilise and knock down the fire.
And whilst, yes, the firemen do spend a lot of their time training they dont just go "Oooo flames. Must. Squirt. Water..." They train for a wide range of scenarios using real incidents and shared experience to inform their training. Many of those guys could tell you more about a fire spreads and the flammability of your aircraft than you. Bear in mind also that many of the airport firefighters were highly experienced local authority firefighters and have fought more real fires than you can imagine.