What-if games don't provide great insights in cases like these. Trust me, if it worked at these scales, you'd hear about it.
The EV on renting and holding substantially improves if the housing market takes off like a rocket. It might not work in your market, but that doesn't mean it doesn't exist.
Black Rock was buying entire subdivisions developed for the purpose of being sold to investors. They were basically large scale apartment complexes. That's wildly different than buying up random homes throughout a city.
Zillow had to give up last year and showed a $300 million loss, and now Redfin is too. I'm not saying it's impossible, but SFH flipping doesn't scale well at all.
"Locally, NAR data showed 38% of single-family properties purchased in Harris County in 2021 were bought by institutional investors. Property data from the Harris County Appraisal District shows nearly 7,000 homes in Harris County as of June are owned by five NRHC members and their subsidiaries."
https://communityimpact.com/houston/bay-area/city-county/202...
NRHC includes the aforementioned Blackrock. Your quote says the top 5 SFH companies own 7,000 homes in Harris County. A county with 1.6 million homes. The sexy headline of 28% of all homes being bought by institutional investors says an LLC is an institutional buyer. It wasn't Blackrock hoovering up all these homes, it was smaller shops and normal people flush with cash and leverage.