I found this quote from JeromeGradskye on the subject, but which of the two scenrios I posted above is the correct one is unclear from this post. Perhaps he could clarify his remarks :)

There are some fairly subtle game balancing facts involved with the animations, which i should probably mention. For example there is only one attack per animation, so the length of the attack animation determines attack frequency for that troop type. The attack delay values in export_descr_unit.txt are used to balance this, so that it doesn't become too restrictive for artists.