"Mounting it with the hoses exiting the bottom of the pump/block module" is the bottom of the CPU/6 oclock, correct?
There's nothing correct about it, as it doesn't matter.
It could be an aesthetic thing(to avoid upside-down or sideways cpu block logo), or they heard something from somebody, who heard something from somebody, etc, and the actual reason for doing it was completely lost.
What matters is what part is the highest point of the cooling loop.
If the radiator is at the top, hose alignment doesn't matter and neither does the pump - except with units that have their pump integrated in the radiator; top installation is a no-no for those.
Front radiator, hoses running along the top: if the pump lasts long enough, the user will start to hear noise at the top of the rad, caused by the increased air volume collecting there. Nothing alarming, just annoying.
The user will then be forced to flip the rad around(if it even fits) or move the rad to the roof(again, if it fits). 360mm and larger can be inconvenient for front installations because of this; imagine someone with a Lancool II Mesh, and their front mounted 360mm has starting making noise.
They can't do a top mount, because 240mm is the limit up there, and they might not be able to flip the rad at the front, because the cooler's hoses aren't long enough, or a large gpu is in the way.
Front radiator, hoses running along the bottom: nothing to really complain about this one.