That is sorta the reverse of what the QLC drives are doing, in that they treat the cells as a lower density cell which is faster/etc until the drive gets to the

That is sorta the reverse of what the QLC drives are doing, in that they treat the cells as a lower density cell which is faster/etc until the drive gets to the point where it needs to use QLC to get the stated capacity. That works though because individual page writes are at least a couple orders of magnitude faster on a QLC than the SMR region on a disk. Shrinking the disk is _MUCH_ harder, there are various enterprise storage arrays which are basically thin provisioned dedupe/etc arrays, and they overwhelmingly just lie about the capacity and throw up big warnings if the physical capacity is being approached. Then depending on which filesystem your running in linux, if they abort writes, there is a good chance the filesystem is damaged (some handle it better than others, and its getting better).