In sprinkler literature, all pressure losses are defined as total (stagnation) pressure loss. A sprinkler K represents a total pressure loss. FluidFlow uses total pressures and total pressure losses which means the we should be using stagnation (total) pressure with sprinklers.
It’s the pressure loss across the sprinkler that determines the flow through it. Static and stagnation losses through a sprinkler are the same for liquids. In a system, stagnation pressures are normally used because of pressure recovery effects.