How should priority be allocated when copying multiple files?

On Apple and Microsoft kit since System 6, and once or twice on NeXT I have seen priority when copying multiple files allocated in what looks like the worst possible way; unlikely to be more efficient than any other, and clearly the most dangerous in the event of any problem.

Neither any detailed specifications of hard- or software nor any of the tags or topics offered could ever matter and what appears here is a bogus 'choice…' wrongly forced upon me. Thanks, Apple!

All three operating systems seem to share resources either equally or at random among all current copies.

Clearly, that would be reasonable if it could be guaranteed that no problems arose… but the point is that on Apple, Microsoft and NeXT kit even single copies sometimes and multiple copies too often fail.

Am I mistaken to suggest that while resources are allocated equally or at random, it is almost guaranteed that any problem will affect all running copy processes.

How am I mistaken to suggest that if resources were allocated first to the smallest file or the shortest estimated transfer those smallest, shortest instances would be more likely to be completed before any problem arose?

Nothing is guaranteed but who believes the 'standard…' method is less likely to cause a problem?

(Clearly irrelevantly, while I was typing that above, my TV asked whether a Priority One Communique was being issued…)