All large silicon chips (dram, CPU, GPU, FPGA, SSD, etc) are built with spare sections to replace non-functional ones. A 6 core CPU could be really only 6 but could also be a disabled 8 core when not enough people buy the more expensive 8 core, and they built too many of them. GPUs can be the same, but there are a dozen different functions that could be broken, so they sell it as the next lower SKU. For example, mining chips don't need HDMI, so if HDMI is broken, normally you would toss a 99% good chip. Contracts for digitally controlled goods need proper consumer protection. Tesla just happens to use the feature a lot. Much cheaper to lose 30kWh worth of raw material that might not have passed qualification, and sell it as a 60, than pay for inventory, scheduling, and swap/configuration stations on your assembly line.
Also, if rumors get out that SKU xyz CAN be overclocked or unlocked 10% of the time when a higher chip is used, people will buy and return 9 cards before getting the bonus, causing lots of grief to the entire supply chain and 9x packaging/refurb costs, and then have to sell as open box at a lower profit. Not gonna happen. These locks are heavily encrypted, or physically unaccessible.
Not having that extra space will dramatically lower the lifespan and reliability of the drive. Same with these batteries.
They just need to be honest about what they're selling.
I have a Samsung SSD. How do I know how much to overprovision? 100Mb? 200Mb? 1000Mb?? How would I know?
When they sell an SSD as, say, 2Tb but then I'm expected to assign 20Gb of that just for reliability, that's materially worse than a drive that advertises 2Tb but doesn't count the overprovisioning. But they're both advertised as 2Tb.
If they're selling a 2Tb drive, it should work as a (reliable) 2Tb drive.
Just like hard drives that manage bad blocks themselves.