According to tech-journalists is the 256 GB SSD in the new Mac Book Air slower then the 512 GB SSD: Article
"While the M1 MacBook Pro and M1 MacBook Air have two NAND chips of 128GB each in its 256GB version, the M2 MacBook Pro – and now M2 MacBook Air – has a single 256GB NAND chip. In the first case, the M1 Macs can achieve faster speeds in parallel, while the latter fails to reach the same SSD speeds since it has only a single SSD."
Therefore it is recommended to buy a Macbook Air with 512 GB or larger.
But: Why is a single large chip slower then two smaller chips?
What's the precise reason?