I feel like the obvious thing to check here is that all chrome processes have terminated between tests. If it's still running some zombie process of course the data would persist.
At least on windows, closing chrome doesn't close the system tray process which keeps Chrome and Gemini prestaged and cached. Wonder if OP is experiencing a version of that on his Mac?
Google and the rest of the billionaire class thank you for ensuring everyone is too divided by red/blue tribalism to ever have enough unity to mount a fight against them. Well done!
That is a likely case. Chrome is their closed source software unlike the Chromium browser.