Your last paragraph needs to be read. And read. And re-read over and over and over and over. You can't read it too many times.
That's one issue the water brake dyno has. It doesn't measure the ability to accelerate. Doesn't mean it isn't an a tool you shouldn't use every time. Like a flow bench, you need to understand what the tools limit is.
Read that last paragraph over and over. RAMM nailed it.
