He did institute it into the series, but that method of splitting the cast and shooting two simultaneously was already a practice in Hollywood. While I'm sure there are others, both Lost in Space and Voyage to the Bottom of the Sea did this to catch up on the schedule and meet air dates in their respective first seasons.Freiberger got around that by creating what was known as the "double-up" episode -
Voyage: The Exile / The Amphibians
Lost in Space: War of the Robots / The Magic Mirror and All that Glitters / Lost Civilization
It's a wonder Freiberger didn't do that on Star Trek, especially with episodes like The Tholian Web and The Mark of Gideon (obviously the completion of those scripts would have something to do with it).