Overall, I would agree with that statement and say that the Forced effect on this enemy should allow for an attack upon entering play, whether it be from the staging area or from an engaged state. The Forced effect says "When Haradrim Elite enters play"...it is not limited to triggering when it is revealed from the Encounter deck.
Without an 'official' answer, I think there's two ways the second part of the Forced effect could be interpreted:
1) The Forced effect of the Dunedain Hunter brings the Haradrim Elite into play engaged with the controlling player. The Forced effect on the Haradrim Elite then triggers, sending the Haradrim back to the staging area where it then makes an immediate attack against the first player. The Haradrim would then remain in the staging area since the Dunedain's Forced effect had already resolved.
2) You work with the assumption that this effect is assuming most enemies enter play by being revealed and added to the staging area and the important part is that they make an immediate free attack, not necessarily that it is made from the staging area. So you could essentially ignore the words "from the staging area" and read it as "When Haradrim Elite enters play, it makes an immediate attack against the first player". The Haradrim would then make an attack against the first player, but also remain engaged with the player controlling the Dunedain Hunter.
Either way, I agree that the favor usually goes to the Encounter deck when there is uncertainty and that the Haradrim should get an immediate attack upon entering play.