Does Windows Explorer and MacOS Finder actually copy files one by one, or do they utilize some kind of batch copying process? If they do copy files one by one, is there a way to enable batch copying?
I tried to find any documentation on this, but can't find a source. Any help is highly appreciated!
And if so, is there a reason that they don't copy them simultaneously?
Yes, I assume they still do.
Jump back in time 20 years; magnetic hard-drives still rule the world and the only time copying multiple files at the same time makes sense is if there are multiple different source and destination (physical) disks. For example; copying one file from C: to D: and one file from E: to F:. This would be faster if done simultaneously. If you start this as one operation in Explorer, it is not smart enough to do them side-by-side because this scenario is rare, the common case is a shared source and/or destination.
The same applies today, there is a bottleneck somewhere, either the drives themselves or the bus that connects devices together and you are not going to gain much by trying to be smart in the majority of cases.
Explorer is slow because it tries to estimate the time remaining and because of the progress bar. robocopy is much faster...