That's not the same thing. The classic formulation is saying that for God, existence is essential, while other beings (not god) do not essentially exist. Spinoza is arguing that God's existence underlies all of existence.
How is that different than Aquinas/Aristotle?
And so does Aquinas: "Article 1. Whether God is in all things? […] Article 2. Whether God is everywhere? […]"
2. According to Aquinas (as you linked), God is "present" inasmuch that God acts on all things ("God is in all things; not, indeed, as part of their essence, nor as an accident, but as an agent is present to that upon which it works"), and Spinoza was certainly more extreme than that. Spinoza thought the world (and everything in it) is a "mode" of God.