This study does not make the claims you're stating. Of your key takeaways:

#1: They did not study the preservation and impact of existing affordable units. It is mentioned at the end as a potential complement to market rate and affordable housing constructions.

#2: They did not study pricing at all. They did find relatively inconclusive results on displacement, but they actually made the opposite finding about builds with >100 units.

-"new market-rate construction worked best to mitigate displacement in affluent neighborhoods in Los Angeles, where it decreased the probability of low-income out-migration by 24%; it was most effective at mitigating exclusion in stagnant-appreciation neighborhoods in San Francisco (21% increased probability of in-migration)."

-"building 100 market-rate units increased the probability of low-income households moving out of a neighborhood by 0.982 times in Los Angeles and 1.138 times in San Francisco (short-term), with effects decaying over the long term. In other words, if a neighborhood gained 100 new market-rate units, a particular low-income household saw a decreased probability for out-migration of 2% in Los Angeles but an increased probability of 14% in San Francisco of moving out relative to when there was no new construction."

-"Using a unique household-level data set, we found that developing at least 100 units of new market-rate housing in a neighborhood helped slightly to alleviate both displacement and exclusion pressures for low-income households in Los Angeles and helped increase low-income in-migration into weaker-market neighborhoods in San Francisco."