The key aspect is that such memory generally works on a "block" level so making any smaller-than-block write on a SSD requires reading a whole block (which can be quite large), erasing that whole block and then writing back the whole modified block; as you physically can't toggle a bit without erasing the whole block first.

So if large sequential writes mean that you only write full whole blocks, that can be done much faster than writing the same data in random order.