Few SSDs can sustain such a speed for a long time. After they exhaust their temporary SLC cache they drop to much lower speeds. SSDs that have accumulated a large amount of writes might also make large pauses at random times during writing, for garbage collection. Good SSDs remain faster than HDDs even in these circumstances, but they are nevertheless much slower than when benchmarked for short times while they are new.

Note how, in the graph, even the worst-performing SSD stays above 500 MB/sec sequentially for an indefinite amount of time, while the parent post claimed SSDs couldn't even do 200–400.

You can get SSDs without such issues. At least for the kind of long sequential writes followed by deletes where HDD are are even vaguely comparable, good SSD’s can maintain very close to their theoretical maximum speeds indefinitely.

They only really slow down in usage patterns that trash traditional HDD’s, which have much worse disk fragmentation issues.

And that's why you buy 2-bit MLC, which can sustain these writes forever. Like e.g. the 970 Pro.