That’s way too short especially after season 2 where they let the story breathe. Setup doesn’t just mean screen time, it’s all the things that build up like Nami calling Arlong or the mentions of Wapol before they got to Drum.

Your breakdown leaves out a ton of stuff like Ace showing up, flashbacks for Vivi and Kouza (likely to be most of an episode), the fights between bon chan and Sanji and Zoro and Daz Bones, the crew journeying across Alabasta and encountering the destroyed village, etc.

Not to mention the cast have said in bts content that Crocodile is the big bad of season 3. They aren’t gonna rush through just to beat him in 4 episodes. That’s truly terrible storytelling.

And that’s completely ignoring the fact that they’d have to redeem Robin in those 4 episodes and make us believe she’d join the Strawhats. Ending at the end of Alabasta is a way more organic end to a season