I should have been a little more clear when I was referring to the "majors". I was simply categorizing people/brokers who can afford to throw around 50k shares to swing the price in their favour before the NR is expected (whether it be in 100 lots or 50k lots you can see in the L2's its put in by the same broker at the same time).

As far as I'm concerned the "average" investor doesn't have that many shares llying around or can't afford to throw $100k + at a junior venture in one shot on a whim. I know in the big leagues $100k is pretty much an average transaction but not so much in the jr's.

Also because the volume is low as you pointed out; it makes no sense to put a single order for 20-50k shares unless you're trying to manipulate the price. On the same lines it makes no sense to arbitrarily sell 100-500 lots into the bid for hours/days on end without a purpose.
I'd understand putting out an order for 50k if there has been a major NR and the volume is consuming everything in site and someone wants in or out, but otherwise there are probably ulterior motives to these actions.
JMHO.