I would not expect to see any increase in writes during a SE. Think that a cycle for a NAND cell is an erase followed by a program operation, so during SE you only have half of the cycle.
@johnw: could you run the endurance test for 20-30TB with trim disabled? I am curious to see what would be WA when the drive has no clue about what has been erased.
Also, about general write performance, it was specified earlier by Ao1 that programming a page takes normally 900μs. 8 dies * 4KiB * (1000ms/0.9ms) = ~34.7MiB/s which is much smaller than what a normal SSD can do. Does anybody know how many pages could be programmed in parallel for one die?