The gameplay might be finished but the player skill isn't, since games usually get harder and harder or more complex the closer you reach the end.I'd say the "ripening banana" allegory works for the now-popular early access model but not episodic games. Theoretically, the gameplay is finished with episodic releases, further episodes just get you new content and the "full" game is equal to the sum of its parts.
If I have to play a bit now and end it then wait months to play the next bit and it is harder and/or more complex, it will take a toll on my skill and I will lose time to get as good as I was already at the end of the first part, then repeat until all episodes are released.
Imagine playing a full game and play 5 hours of it then stop for months, then come back and play 5 more hours and then stop for a few more months and so on. It would make the game boring and depending on the type of game we would have to relearn how to play again and again.
I never buy things in parts, games I think I will like I wait until all DLCs and "parts" to be released as a "Complete Edition", because Episodic stuff or playing now and then only get the full product later really sucks for me.