Isn't this normal? I thought that's how it typically works when an employee leaves a company with any method.

This is the unfair part. Quite often salary is reduced with the excuse of having stock options. So this is more like a cut in earned salary along with getting fired.

That's the definition of "unvested"

Anyone evaluating compensation and stock options should understand vesting periods and what they mean so they're not surprised by something like this.

Ouch. Imagine being let go just a few weeks from vesting. Doesn't seem fair to let someone work for months and months in anticipation of their big prize and then yank it away at the last minute.

This is standard in every tech RSU vest schedule I have seen.

That's what the word "vested" means.