Rato Borrachudo is live streaming his Series S disassembly right now. It’s also a standlone drive, it’s not Western Digital and they said it’s the same manufacturer of the Surface SSDs. He is about to install a larger Samsung SSD drive to see if it works.
They also said people yesterday thought the Series X SSD is gen 3 because they matched the model number of the Series X SSD with another one on WD site that has a similar model number. However, they said it has one different letter on the X model, which differentiates it from the gen 3 people were thinking it was the same. They said it isn’t, it is gen 4.
If anyone wants to watch his experiment with the Samsung SSD, here is his Twitch link (it’s in Portuguese, since he is a fellow Brazilian, but you can watch it anyway): https://www.twitch.tv/ratoborrachudo