People leaving is not the same as displacement. Many people chose to leave during the pandemic for a variety of reasons, including tech workers moving away to work remotely.
After all, why stay in a city when everything is closed when you can get the same experience cheaper somewhere else?
Any time window that includes 2020 is going to include very strong pandemic-related effects.
All you provided is evidence that people moved away from San Francisco during the pandemic. We all know that. Many of the people who left could have afforded to stay and chose not to. That is not displacement.
Proof of displacement requires demonstration that people left SF because they could not afford to live there anymore. It's really that simple.
Techies with six-figure incomes leaving town to move back in with their parents during the pandemic doesn't count as displacement.
After all, why stay in a city when everything is closed when you can get the same experience cheaper somewhere else?
Any time window that includes 2020 is going to include very strong pandemic-related effects.