The parse_args doc says " args - List of strings to parse. …" The proposal is to add something like ‘, in normal order’ to the end of the sentence. The reason is that parsing each arg has a side effect and that the net effect of parsing all args may depend on the order of parsing.
I suggest opening a feature request on the tracker. Reference this discussion. The consensus here, I believe, is that the behavior should never change, so that the order should be guaranteed. The main issue is whether it already is or not, which is to say, whether the addition would be redundant or not. Making the request minimal, such as 3 words, makes the bar for adding it relatively low. Let the few coredevs involved with argparse decide.