What you are saying is incorrect.
Let's go back to the announcement of castings per Elon:
“The Model Y made here and in Berlin will have a cast front body and a cast rear body,” Musk said. The Fremont-based Model Y carries a “cast rear body, but not a cast front body,” Musk said.
Musk said Tesla also planned to outfit the Texas and Germany Model Ys with a “structural pack” containing 4680 battery cells. He said this offered both mass and cost reductions.
“We’re not counting on that as the only way to make things work,” Musk said. He said the OEM had developed a backup plan involving a nonstructural battery pack with 2170 cells, but it ultimately desired to use the structural pack and 4680 cells at scale production. This was the lightest and cheapest option, he said.
Again, all MYs being delivered from Austin are 2170s...that may change in the future, but hasn't, yet.