There are two different things when talking about application behavior versus disk behavior.

>wait for the whole list to finish rather than blocking on every tiny file.

And this is the point. I can make a test that shows exactly what's going on here. Make a random file generator that generates 100,000 4k files. Now, write them on hard drive with other data and things going on at the same time. Now in another run of the program have it generate 100,000 4k files and put them in a zip.

Now, read the set of 100k files from disk and at the same time read the 100k files in a zip....

One finishes in less than a second and one takes anywhere from a few seconds to a few minutes depending on your disk speeds.