Random 4KB writes have always been a problem for JMicron's controller architecture. The company powered some of the first affordable consumer SSDs, and over the years it has worked hard to improve its performance in this discipline. Although we measure 4KB random writes in IOPS, this particular measurement is really about latency.
A single log file update to one program can bring your system to a crawl until the task completes. Native command queuing allows for up to 32 outstanding commands, though only one can run at a time. It it hangs or takes longer to process than expected, your experience is diminished. High IOPS performance translates to low latency.
The JMF670H is now on par with the random write performance available from several mainstream and even some premium SSDs on the market today.