BurstarIt's not 'all heat'. It pulls heat out at a set, admittedly very high, rate until discharged. If you're at 20000% heat and pop a heat sink you'll be at 19500 or something not 0 by the time it's done.
In a roasting T9 charging it's FSD while bordering a type A star a heat sink will barely cause the heat needle to move.
Interesting, I’ve yet to have a heatsink fail to drop my ship’s heat to low single figures, if not to zero. That includes falling foul of star exclusion zones and burning off caustic Thargoid snot.
If one reached 20000% heat I suspect your ship would be full of molten modules, including heat sink modules. In that case I suspect the point you make would be somewhat academic