Gravity sling shits were typically only done when a ship needs to get to a safe jump point. now this is only seen with the UNSC. This is because during and before the human covenant war the UNSC has slipspace drives that had an accuracy of +/- hundreds of thousands of kilometers. Jumping directly to the planet could land you inside the core of the planet or inside of a star. Now with more accurate drives exiting slipspace in system is a whole lot less dangerous
It was theorized by Cortana that you might actually not be able to come out of slipspace into something. The object and the exiter would both move out of each others way. This is all conjecture from her, however they do exit into a ship debris field and non of the debris got phased into the ship and instead surrounded the ship further increasing the chance that her theory was correct, you can't come out of slipspace inside something.
Ascendant Justice winked into existence within the debris field in high orbit around Reach. There was, however, no ultravi-olent explosion as the atoms of the flagship overlapped with the matter of the scrapped ships the Covenant had herded together in space. Either Slipspace jumps prevented such occurrences from happening, shunting the incoming ship to the side like water that flows around a river rock ... or she had borrowed some of the Master Chief's probability-bending good fortune. Hundreds of wrecked ships, human and Covenant alike, tum- bled lifelessly about her, their net trajectories suggesting that As- cendant Justice had just nudged them aside. If she'd had more
time, she would've designed a set of experiments with drone ships to test out her displacement-luck hypothesis.
But that is mostly just a theory however there are no instances where a ship did explode from exiting inside something.
Contrary to this, in the Forerunner books they predicted incoming slipspace exits and shot things (asteroids) in the way. When the ship exited it was forced back into slipspace by the object or destroyed.
So begins the clench. While the re-emerging enemy forces are most vulnerable, still surrounded by a haze of alternate realities, the Falchion orders a carefully pre-positioned series of stabbing harrier attacks. The cloaked harriers engage first not with obvious and traceable beam weapons or projectiles, but entrained local asteroids, delivering them through gravity slings into the emergence field of each arriving enemy vessel.
The asteroids interfere with the collapsing function of each emerging ship; in effect, either forcing them to abandon the transit, or to combine asteroid mass with the ship's.
The result: half of the arriving vessels dematerialize in brilliant flashes, while the other half desperately reposition by a few thousand kilometers. This affords a multi-pronged force of uncloaked harriers opportunity to engage in open beam attacks, swiftly destroying another third.
So in this case there are explosions. However I think because the asteroids are shot into the exiting ships while they are still... exiting... this wouldn't happen regularly, as in if you attempted to exit on top of an asteroid rather than have one shot into you.
