He says "powered by or funded by Google". Firefox depends on Google financially, most of the income of Mozilla comes from Google paying for being the default search engine.

They try to diversify their income (Firefox VPN, email alias service, etc.), but anything they try gets a huge backlash from the community, and still small compared to the the money from google.

Google is Mozilla's biggest source of income, and google developers have actively contributed code to the Firefox engine.

So you decide for yourself what level of independence you assign to it.

Firefox gets tons of funding from Google, and their code is quite frankly humongous. From what I understand, it's extremely hard to get the gecko web view engine to work. In another browser, unless it's a fork of Firefox, unlike Chromium where you can just redesign an entire browser around it.