Yeah, that is correct. Firefox and chrome will return the order of the file picker. So unless you already sorted it in the file picker, the ui must somehow add an extra step before uploading as you cannot get the data of their selection order.
If that was your case, then it is absolutely a bug that can be fixed on the client side without adding new features.
Yeah, the problem is that concurrent image upload is splicing the array. That means there is a batch. Each “first” in their batch will be processed first leaving the actual 2nd image waiting for the actual 1st to be finished, but the 4th has begun uploading.
Edit : Sorry, can’t really help writing code as I am on mobile but it is funny to think that actual development can take places anywhere for open source software.