Two things.Role play defines events and THEN mechanics resolve the outcome
is very different from
Mechanics defines the events and THEN the player provides narrative to connect the dots.
First, AD&D has elements of the latter - it is quite explicity in the 1st ed DMG that a saving throw is to be rolled - a purely mechanica process and then, depending on the outcome, a narrative is provided to join the dots.
Second, 4e has elements of the former - it is quite explicity in the 4th ed PHB and DMG that in a skill challenge the GM describes the scene and the players describe how their PCs are responding to it, and then skill checks are worked out, DCs assigned, and rolls made.
AD&D combat can be (and in my experience frequently was) played in the second mode - players announce moves, attacks etc all in mechanical terms, deliver and take hit points etc, and only at the end are the dots joined - the narrative becomes one of "we won the combat" or "we lost the combat".
4e can also be played in the second mode, with one exception - because movement is so mechanically integrated into combat, there is at least one aspect of the ficiton with which players (or, at least, my players) remain initimately engaged, namely, the position of PCs, enemies, terrain etc.
I'm a very firm proponent of the notion that there are big differences between AD&D and 4e. But this notion of the priority of fiction to mechanics or vice versa is (in my opinion) mostly a red herring as far as those differences are concerned, because it mostly concerns players' initiation of action for their PCs - and in this respect I don't think 4e is radically different from more traditional RPGs.
Rather, the differences obtain in what is understood to be the relationship between ingame causation and actual causation in the mechanical system. But (i) this is more obvious to the GM than the players, and (ii) it happens much more at the encounter design state - setting DCs, choosing enemies etc - and at the conflict resolution stage - how many successes are enought for victory?
These aren't differences connected to player initiation of action.
And as far as actual play experience - I'm still waiting for someone to respond to my actual play example and tell me where I violated the rules, guidelines, or standard practices of 4e.