With today's trading platforms, it would not take much effort to put in 10 2500 shares orders at the same price. Even for retail.
It would also be easy to "chain them together" so that order 2 was contingent or order 1 executing, order 3 contingent on order, etc.
Not saying that is what happening, just observing that doing what you mention would not be all that difficult even for a not overly sophisticated retail guy.