What? “Opening short positions then pumping and dumping to trigger the shorts” doesn’t make any sense at all. You’re saying they opened a position that profited if the price went down then they bought to raise the price
In this case they buy slowly to avoid artificially propping up the price, then sell all at once to artificially drop the price, only momentarily. They don’t have to cause the entire price drop through selling everything they acquired, they just have to move the price down enough to trigger stop loss orders that they know about.
With this strategy they can accumulate assets while also taking profits on the shorts. It’s the retail investors who put in market orders or stop loss orders that get taken for a ride.
In their role as market maker they have all the information needed to minimize the risk of this strategy.