No I quite get the point, I'm saying the point is absurd. It's quite obvious if you change the system the system changes. But if the system is at equilibrium, the system is BY DEFINITION balanced, and balanced things are stable. If you change the system so it's out of balance, then yes it becomes unstable/dangerous.
If a long-term track record has yet to allow the boiler to explode, and knowing the mods that MongrelVigor is using, the water system is less likely to fail than the reactor is to fuck up and send too many neutrons in one tick to a single boiler, which can explode "author safe" boilers too. That means that yes, a >450 boiler is SAFE if it's been going for even ingame months (at 10 hours per in game month of 30 days), unless something about the system changes. Obviously you could have insufficient water supply, but that's in NO WAY unique or the fault of the >450 temperature. In Mongrel's case (using Pressure Pipes), he WILL NOT run out of water. One source puts out more than enough for a Tokamak IIRC, let alone a lower tech reactor.