Comment by joshspankit

From my understanding, the thing that’s slow is writing data to “permanent storage” (aka the layer under all the caching).

Some storage tech is just slow at that, and manufacturers muddy the water by rating some (SSDs|Micro SDs|whatever) in GB/s overall when much of those big numbers are a combination of caches and trickery.

I would not be surprised if Apple is using a tech that just has slow write speeds in trade for fast read speeds since most Apple users will be happy with faster read speeds.