Check out the context of Exodus 33:20 -
Jehovah was already talking to Moses face-to-face. Jehovah was in a materialized body. Moses then asked Jehovah to see Jehovah's full heavenly glory, which was when God responded by saying it wasn't possible for a human to do.
Obviously it was possible for a human do see God in a materialized human form, but that wasn't what Moses was asking about when God gave the answer at Exodus 33:20.
Moses was talking to Jehovah face-to-face. Just like He did in the garden of Eden with Adam and Eve.