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.
I've found the free version swaps away from pro incredibly fast. But our company has gemini but can't even get that - we were being asked to do everything by API key.