The latter interpretation of warp collisions would make more dramatic sense, yes.
Perhaps our only reason to believe that warp fields themselves would release major energies to "realspace" on impact, rather than harmlessly dissipate them to "subspace", comes from the TNG episode "New Ground" where a self-coherent, surf-like warp field (a "warp soliton") pushed physical objects along at FTL speeds but was said to shatter planets if allowed to impact with them. But that was apparently with much more energy than featured in the warp field of a mere starship or missile or similar object.
We have also sometimes seen that while warp fields can be maintained close to massive objects (unlike in universes like Asimov's Foundation one or Niven's Known Space, where nearby mass makes the use of FTL engines impossible), warpships become slow as molasses near such objects. Warp ten in ST4:TVH looks like crawling when taking place near the Sun, for example - and warp within Earth's atmosphere in the same movie doesn't seem to amount to too many Mach numbers...
So perhaps an attempt at ramming a planet would be thwarted by the ship losing all its warp energies already on approach, much like a Hägar the Horrible -style, man-hauled battering ram would be useless against a fortress situated on a high hill, the climbing of which would take all strength out of Hägar's men and all speed out of the ram.
Ramming a fellow starship might of course be a bit more successful, then. But possibly two warp fields merging would result in an uncontrolled release of energies - yet not inward towards the "victim" ship, but in so many directions that the impact would just throw the two ships in different directions and out of warp. This even if the ramming happened at high speed differential, say, a ship at warp nine ramming a ship at warp six.
The fact does remain that planets have not been warp-rammed, and ships at warp have not been rammed by ships at warp. Yet sublight ramming between ships seems to work fine, even when shields are in use - and Riker did attempt to ram a sublight Borg cube with his own starship at warp, suggesting that such a maneuver makes tactical sense somehow.