I think he's referring to Nimble Strike.
And there are still differences between a move and a shift. If the Ranger is wearing Scintillating Armor, for example, his ranged powers do not provoke, so Nimble Strike by itself would not provoke... but the move would, where the shift does not.
If the Ranger is marked by a Fighter, then the shift will trigger a Combat Challenge attack, while if it were a move, it would not; and while the move would provoke an OA, the Fighter probably already used his OA on the ranged-power-in-an-adjacent-square provocation, so the move would be advantageous for the Ranger compared to the shift in this case.
Nimble Strike as written, and Nimble Strike altered for a one square move, behave differently... so asking "Why is it a shift?" isn't really pertinent; it is a shift, because it was written as a shift.
-Hyp.
Yes.
However the question of "why is it a shift"
is relevant in terms of RAI because:
(a) It's ranged only ... the melee only power hit and run is designed to avoid taking an OA.
(b) If using the power provokes, instead of that "attack" provoking, using a shift to avoid the OA, the PRIMARY purpose of shifting, is pointless. There are specific exceptions where interactions with magic items or feats or racial abilities make things different ... but ultimately you have a power that lefts you shift to avoid an OA ... but it doesn't actually avoid the OA.
Basically ... it seems in many ways to be a power that THINKS it is doing something it doesn't actually do.
See also: the pact hammer whose property is that it let's you do curse damage on melee attacks ... which you could already do, but someone obiously didn't realize when designing the power.
Talking about RAW ... it shifts because it says it shifts.
Talking about RAI though, it is relevant to ask why.
And, considering that from the initial books to newer books they've found ways to "correct" powers so that "charge as part of the attack" has become "use this power in place of a basic melee attack as part of the charge" means they are still in the process of fixing effects they misworded initially.
By the way, by RAW, you can use this to shift adjacent to someone and then attack without provoking [assuming you weren't adjacent to anyone when you initiated the maneuver, before you shifted], perhaps intending to get prime shot? Since it's using the power, not "attacking", that provokes?