[g.willikers]

We really don't have any way to measure pressure.
While velocity and pressure are related, they aren't always directly relative to one another.
There's variables that can cause increases in pressure without an increase in velocity.
Maybe high pressures can be noticed, but maybe not.
Besides just getting an unexpected surprise, getting into the habit of mixing powders could result in mixing two different powders by mistake one day.
Oops.
My own experiences show that different batches of the same powder, bought at different times can, indeed, have different results.
No hugely, maybe, but definitely measurable.