To expand on the variation in the 4k write performance at QD1 that I could see following repeated testing using AS SSD. (I observed variations in write speeds from 30MB/s to 47MB/s)

If a drive is preconditioned naturally or synthetically by writing across the full span of the logical disk it will at some stage start to wear level and swap out dirty blocks with clean blocks previously hidden within over provisioning capacity. This may be why I was able to see a degraded drive suddenly be able to produce better results , which then went on to degrade in the next benchmark.

If that is correct and a reviewer does not precondition a drive by writing to the full raw capacity it might result in a benchmark result appearing better than it should.

This raises a few questions for me. How many writes are needed before the blocks get rotated and how many blocks get swapped over at any one time?

I'd guess it varies between different SSD's but without this knowledge how can you be sure you are benchmarking only preconditioned blocks?

If a drive is in constant use does it allow data to be written to clean over provisioned blocks and then swap the block over at a later date? If so that would also perhaps inflate a "used state" benchmark.