Strictly speaking that depends on the definition of meat, which for some is limited to mammalian meat. Others prefer to call vegetarianism plus fish pescetarianism, vegaquarianism, or pesco-vegetarianism.

He said specifically that eating fish is not vegetarian, this is 100% an accurate statement, you can choose to define the word "meat" however you want but the textbook definition of vegetarianism does not include fish.

But semantics don't really matter if we're talking about vegetarianism for sustainability of the planet.

Define fish as meat or not, that is, in my understanding, a currently unsustainable model.