I don't know anything about it. I wanted to know more and that was the only decent vid I found. I think "mega" is key and it allows much bigger size stuff to be made in one piece.

This is what Tesla calls Gigacasting. It's just a bigger version of die casting, with higher pressures and other tweaks to make sure the mold fills up completely before the aluminum solidifies. Lots of auto makers are using similar technology today because it speeds up the production process and can make cars lighter. But it also means that the car chassis is basically impossible to repair after a crash.

https://www.theautopian.com/a-chinese-company-just-gigacasting-an-entire-underbody-and-can-we-not/