I'm more than okay with this mediocre showing. SATA is starting to become a crippling bottleneck but the sub-10c/GB is great to see and there are some pretty common use cases where this will be one of the best options. The fact this delivers a consistent write speed to keep up with the SATA bottleneck is another welcome bonus in this cheap market segment that is otherwise served by abysmal drives crippled by DRAMless QLC.
Gaming laptop is one obvious choice - they can benefit from a light, large, fast, shock-tolerant storage library in a 2.5" form factor.
Portable SSD is another one, since this in a USB3.2 external enclosure will be one of the cheapest ways to carry around this capacity in relative safety.
The real issue is that 2.5" is a dying form factor. ATX cases are getting bigger, ridiculously so, and laptops are getting so thin that most of them ditch 2.5" bays for a second M.2 slot instead. So this Sandisk Ultra 4TB is useful in a few scenarios but I think we'd all like to see WD/Sandisk bump up their WD Green (SATA) M.2 drive to larger capacities. The M.2 2280 WD Green tops out at a paltry 480GB and the only M.2 drive under the Sandisk brand is the X600 which tops out at 2TB also.