Omniscient POV is close to Third person Limited but varies mainly because an omniscient narrator can switch to a different character's perspective any time, and can simultaneously share with the reader anything and everything about that character and any other character. But despite any periodic switching or closing in on characters, the narrative voice remains that of the omniscient narrator - not that of chosen characters.
Omniscience lacks the enforced discipline of Third Person Limited, but still requires focus and control to be effective. The temptation to ramble on and jump about -simply because one can- has to be controlled.