That document is mostly conspiracy nonsense. Wholesalers don't need to push the price around to make money. Most retail trades are tiny, uncorrelated with future order flow, and don't have short-term alpha behind them. The wholesaler will make money filling them at the NBBO with a small improvement and holding the delta. When you can't be hit by hedge funds slicing their massive order into a million pieces, HFT quant algos or arbitrage traders, and don't have to compete to be first in the FIFO queue, making money buying the bid and selling the offer is easy money.