It's always safest to follow the manufacturers instructions instead of what someone tells you.
There's folks who will say anything at any time, without the foggiest notion as to what they could be doing to the questioner.
I've never seen or done a power-on dive test.. the way you describe it a pitch-up is inevitable, as the power-off gliding speed will be much less than the speed in a powered dive, so the plane has to pitch up due to the excess lift.
Dive testing power off will locate your c.g. correctly. A mild automatic pullup after doing the dive is safest.
Lots of climb with lots of power is a good thing.