I think it's less about grammar and more about people trying really hard to make the spell say something that it doesn't. The spell clearly states that it uses your Action to make an attack. If it meant that you could use it with extra attack, it would state Attack Action somewhere in the spell.
I'm not even against it being used with extra attack, but people are really reaching to say that's how it works anyway when they can instead just say that they've changed it to work with the attack action.