It doesn't, it's not "1000 Gemini Pro" requests for free, Google misled everyone. It's 1000 Gemini requests, Flash included. You get like 5-7 Gemini Pro requests before you get limited.
Your link shows the free tier gets 100 Pro requests per day.
That matches my experience with a free account. With Gemini CLI it doesn't seem to matter if I log in with a Google Account or use an API key from AI Studio with billing disabled.
Yesterday I had two coding sessions in Gemini CLI with a total of 73 requests to Pro with no rate limiting.
After that it's bumped down to Flash, which is surpisingly effective in Gemini CLI.
If I need Pro, I just swap in an API from an account with billing enabled, but usually 100 requests is enough for a day of work.