Pretty sure that Apple isn't manufacturing NAND chips. Now it might be hard to procure the 128GB chips, so Apple may be at the mercy of suppliers, or it might just be cheaper to buy a 256GB chip (and suffer slower perf).
Apple may not manufacture them, but they don't look to be off the shelf components either. So maybe I should be writing "Apple has stopped ordering the 128 GB chips and removed them from all current designs".
This has been coming for some time, the refreshed 14" and 16" Pro models already had their base capacity bumped to 512.
