Well, that's blatantly false...
A well-known anticompetitive tactic is for a big player with a vast bank account to move into an area and eat losses while waiting for their competitors to starve. Well observed in the 90's movie rental market, so certainly real.
You don’t lower your prices on the off chance a competitor might enter the market in the future. You wait until they have invested capital but before they start making profits and are at their most vulnerable.
Selling below market price != selling below cost, which is a prerequisite for it to be anticompetitive
The statement further up should have qualified it as "scarce commodity". Then it is correct.
To successfully perform dumping, you have to have access to excess supply capable of disrupting that market.