Actually, I think I pretty much do. [For those other than me and Dave: We were discussing whether Apple blocks 3rd-party slotted SSD modules; I contend they do.]
Just to verify, I contacted OWC about this. As I mentioned before, they're one of the best-known experts on producing 3rd-party upgrades for Macs. And they confirmed they looked into this and found that, as of this time, it was not technically possible, because Apple doesn't allow it.
Here's the transcript of the chat (I edited out my name and the name of the OWC rep, but otherwise the content is unchanged). I asked if the reason OWC doesn't sell 3rd-party slotted SSD modules, for the Studio or MP, is because this is blocked by Apple. He said yes:
OWC: Thanks for choosing OWC for your technical needs. I would be more than happy to assist! Just to begin with correct they made it non user changeable so that is not something we can currently offer. If we eventually find a solution for that we will post about it but as of current is unlikely
Me: ....and just to clarify, when you wrote "non user changeable", you meant non-user changeable with 3rd party solutions, right? Since these are user-changeable on the MP when you buy the part from Apple.
OWC: Correct
In addition, if you take a closer look at that SSD upgrade thread you linked, you'll see they were only able to do storage upgrades on the Studio by soldering higher-capacity NAND onto existing Apple-branded slotted SSD modules. No one is able to make 3rd-party slotted SSD modules, because Apple blocks their operation. The only workaround is to use soldering to upgrade Apple-branded modules, and the only way you can get those is by pulling them from a Studio, or possibly through Apple's self-repair program.
That's not going to block 100% of customers from upgrading them, but it will block 99.[many 9's]% of them, making it a block for all intents and purposes.
Here's a dedicated thread on Mac Studio storage upgrades:
Hi, just tested yesterday an upgrade of a plain basic MacStudio M1 Max (2022) from 512GB to 4TB. and it works : take off the 512 GB NAND insert in the right order the two 2TB NANDs inside the slots restaure the MacStudio bridgeOS with another Mac and AppleConfigurator et voilà ...
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