They are as independent as Mozilla is from Google. So they're not the same entity; but in practice they take orders from Eth foundation because they're funded by the Eth foundation.
Alternative interpretation is that while funded by the foundation, they follow what they think the community overall would like to follow, which is the protocol known as Eth 3.0. "Taking orders" being following specifications written by people who seem, after reviewing their work, to have a good heart in the direction of the project.
Jumping to "they are doing X because of Y" seems a bit intense, and would like to see how you're getting there.
What would it take for you to see it differently? That one of the clients diverge from the specifications to do their own thing? That's not in anyone's best interest either, so unlikely to happen.
