I could be wrong, but I think that is what I remember from a YouTube video I saw a few months back.
Musk had an Italian company build a casting machine so they could cast the frame in 1 or 2 pieces. The model Y made in China is cast in one piece. That is how they can assemble them so fast.
The Giga press made GM, Ford and Sellantis obsolete.
They lack the brains to compete