I got my green card before I got married (not through marriage).

I'm still eligible to apply 3 years after getting married even if I haven't been a permanent resident for 5 years at that point.

But I couldn't file early because that's only when the limiting factor is when you got your green card but not when you got married. I don't think that's clear on the website since it says:

You may file Form N-400, Application for Naturalization, 90 calendar days before you complete your permanent residence requirement if your eligibility for naturalization is based upon being (...) Permanent resident for at least 3 years if you are married to a US citizen.

That was the basis under which I was applying, but I still couldn't file early.