Details from the SW universe are not always consistent with other statements from other SW sources, or thought out from a particular theory of how the science might work. We can reconcile what we can, but may have to accept that some things contradict and must be regarded as inaccurate, waved away, or just anomalies.
I think the best explanation for hyperspace is some form of travel beyond our typical 4 dimensions. You might consider it some form of worm hole theory, tunneling through space, or "wrinkling" space.
Any of those explanations actually would not necessarily result in the objects traveling in hyperspace to ever reach anywhere near relativistic speeds -- in the sense of the normal-space kinetic energy that would imply.
Entering this extra-dimensional space wouldn't, therefore imply even approaching the speed of light, kinetically. Neither would exiting. I would note that ships that come out of hyperspace appear to practically slam to a stop.
So, I don't think you can assume the exiting hyperspace would give any object sufficient kinetic energy to any special amount of damage. Given that, you'd have to either wave away as inaccurate the reports of exiting too close to planet. Unless something having to do with the size or fluctuation of the extra-dimensional space can have some affect -- perhaps unpredictably (and not always).
Also, if you try to reconcile the difficulty of navigating hyperspace with the emptiness of real space, you may conclude that mass and gravity actually have a far larger impact in hyperspace, so that (unlike in realspace), zipping about in hyperspace is like trying to slip a needle through tons of clusters of close and powerful magnetic fields without it getting pulled where you don't want it.
If that's a fair analogy, then even removing any potential safeguards from a hyperdrive engine (which would presumably attempt to drop you out of hyperspace in advance of a collision), the mass itself may interact with hyperspace in such away that it pulls you back into real space at a certain proximity (not within), perhaps too close to react but still, given the non-relativistic speeds the vehicle is actually traveling, too slow for the impact to do much harm to a much larger body.
All this being said, while hyperdrives have been calculated to allow starships to cross space in the SW universe at effectively many millions of times faster than light, even sublight speeds are nothing to sneeze at, with incredible acceleration and capability of crossing solar systems very rapidly. Those sublight speeds could allow a massive starship to be a very dangerous projectile even at velocities still much lower than the speed of light.
All of this must be made possible by some form of inertial damper, which effectively soaks kinetic energy somehow so that the passengers effectively feel little to no movement. This technology, like artificial gravity and repulsor technology (opposing gravity very precisely), also has many implications.
If starships can have inertial dampers for passengers, why not to mitigate the impact of collisions? Either way, you're soaking kinetic energy relative to an object. Granted, if this were possible, given enough reaction time for calculations of said dampers, then collisions (such as the SSD into the Death Star II, or asteroid fields, or other ship collisions), would be potentially irrelevant. However, I think, given those aforementioned sublight speeds, some form of external inertial damper probably would exist with the capability to at least reduce the impact significantly, and possibly proportionately (i.e., halving the impact kinetic energy, vs. just subtracting a certain amount). Otherwise collisions could still be crazy lethal. Perhaps that's part of shielding?
It would help explain, however, why only energy weapons really matter in SW. Why rail guns can't just be expected to rip through hulls and shields.
- Ships coming out of hyperspace may not be traveling very fast and
have non-relativistic kinetic energy.
- It may be impossible to exit hyperspace in or even extremely close to a sufficiently massive object (though still close enough
for unavoidable collision)
- Inertial dampers or shields may make kinetic impacts significantly less destructive.