I'll sum up this hard truth with an analogy: "You must be this tall to ride this rollercoaster" has nothing to do with punishing short kids. It prevents injury to short kids.
The thing is, letting kids with sub-par K-12 education into higher ed isn't doing them any favors. It sets them up for potentially devastating failure. Many of them will be so far behind that they'll fail within the first year. It's not that they're not smart, or they're not hard workers. They simply lack the foundation that their peers already have. They'll need remedial coursework before they can even try to re-take the standard curriculum. Or they may be able to limp through some basic classes before failing a year later.
Imagine that scenario for all the kids in an entire state.
And to continue your point - you're right that poor kids are punished. They're punished all across the US, but it has nothing to do with whether they're admitted to university. It's because their K-12 schools are funded by local property taxes. Rich districts get good schools with better teachers, and access to better materials and opportunities. Poor districts have few resources, more (on average) parental apathy towards education, and poorer outcomes. Even the top ranked kids from poor schools may struggle when they reach college.
Florida is trying to expand that disadvantage to an entire state. The fact that out of state admission officers will look at a HS degree from Florida the same way they'd look at one from a homeschooled kid isn't a suggestion or a proposal. It's a fact.