There's no reference to them following the TMM rules for the same reason most weapons don't say it: you don't add the standard rules to weapon entries, only violations of them. As the TO:AUE entry says, they're ballistic weapons rather than artillery weapons and are "resolved normally". They thus function as any other ballistic weapon (except for never applying the immobile modifier), including the need to add in TMMs but also the ability to be fired at a hex.
What's different is the AE quality of its ammunition, separate from the weapon. This allows you to fire at a hex and conveniently bypass the TMM of a unit in said hex thanks to the AE rules. So it's not so much that they ignore TMMs as that they sidestep around them by being area-effect; you generally just don't bother firing at a unit directly with them because the hex the unit is in is going to be the easier shot.