For context, they're arguing elsewhere that saying "Zionism is Jewish supremacist" equates Judaism with Zionism, and I hope it's obvious that that's a wild take.
Edit: also, do liberal Zionists not support the maintenance of an ethnostate? Because that's Jewish supremacy, even if they don't think of themselves that way.
But it really isn't the same. "Jewish supremacism" is a specific idea - that Jewish people should hold power in Israel, which really is the guiding ideology of Zionism.