Being a citizen is not relevant to whether it's an extradition. "Extradition is an act where one jurisdiction delivers a person accused or convicted of committing a crime in another jurisdiction". The Ecuadorian embassy doesn't have its own jurisdiction.

They framed it as merely revoking his asylum at which point the UK arrested him. You cannot revoke asylum of your own citizens. Foreign nationals seek asylum.

There are quite a few legal differences between extraditing somebody and just letting an arrest happen.