Correct. Other than the person posting, no one else is going to know what order the photos are supposed to be.
I can't speak for
@gnsteam but I was just testing to see if when I uploaded multiple photos, the forum would keep them in the order I selected, or insert alphabetically by file name. It turns out it's the latter.
But once the photos are uploaded it's very easy to drag and drop them in whatever order you want in your post, so it doesn't really matter.