By the way, if one just wants to get rid of specific planet types popping up via the randomizer, isn't it enough to remove them from GalaxyScenarioDef.galaxyScenarioDef [via modding]?
As far as I can tell, there are no other references to Ship.Graveyard [as a case-insensitive regular expression] except in that file (GalaxyScenarioDef.galaxyScenarioDef) in the planetType lists: WeightedNonIce, WeightedNonIceFair, WeightedRandom, WeightedRandomFair, AsteroidOrDead, AsteroidOrDeadFair, RandomSpecial (but not in RandomSpecialFair), RandomUncolonizable, RandomUncolonizableNonMagnetic (but not in RandomUncolonizableFair or RandomUncolonizableNonMagneticFair), and also included in the catch-all Random and RandomFair.
Ship Graveyard is not however included in RandomTrue and RandomTrueFair lists which only have Terran/Ice/Desert/Volcanic/Oceani/Ferrus/Greenhouse. So Ship Graveyard won't replace a Terran in all circumstances in the sadomizer, but only where non-beefy planets could appear as well. What's interesting is that it can replace a non-colonizable, although not in the Fair version thereof. That's perhaps not so surprising given that it's basically a dead roid with resources.
The big 5v5s used on ICO (Huge Single-System Random Map Fair.galaxy) use basically just WeightedRandomFair and RandomFair for most of the map (except for the roid/moon/volcanic near each Homeworld), so you'll get some Graveyards in those maps, but the probability is low because there are four times as many WeightedRandomFairs than RandomFairs in those maps and [because] ShipGraveyard is only listed once in WeightedRandomFair, whereas [for example] TerranFair or FerrusFair are listed twice, DesertFair/VolcanicFair/IceFair/BarrenFair/OceanicFair/GreenhouseFair three times each, MoonFair/AsteroidFair four times, etc. Other singly listed items (like Ship Graveyard) in the WeightedRandomFairs are GasGiantFair, DeadAsteroid, PlasmaStormFair, and MagneticCloud. So adding Ship Graveyard to that Weighted list does skew it in favor of [almost] non-colonizables by a tiny amount (from 4/38=10.5% to 5/39=12.8%), but is not something to go up in arms against, IMO. In the RadomFair list [which is only sampled 1/4 of the time compared to the Weighted one], the distribution of crappy ones goes from 4/14=28.5% to 5/15=33.3% with the addition of Graveyard; still not a major skewing, IMO.
Of the other lists mentioned which can include the Ship Graveyard, RandomUncolonizable appears in a significant number of scenarios/maps (42 hits), followed by RandomSpecial (29 hits) and AsteroidOrDead (19 hits). Of the randomized lists that don't include the Graveyard, RandomTrue is perhaps the most important, with 76 hits in the galaxy files shipped with the game.
The Graveyard provides an okay level of [intermediate] variation in gameplay IMO, being somewhere between a regular asteroid and an uncolonizable body with capturable extractors (e.g. those of the Space Junk or Gas Giant, called "neutral" extractors in the entity files.) An asteroid takes a long time to pay for its initial colonization price, whereas the Ship Graveyard, while not giving access to resources simply in exchange for antimatter (as the capturable extractors do) has an intermediate cost between those two: AM-only for colonization but credits for its resource extractors. The Graveyard's extractors have higher base rate than those of a regular asteroid, and are [unfortunately] also affected by allegiance in their extraction rate, like those of the asteroid, but unlike the capturable extractors from a Gas Giant etc. The Graveyard's extractors however are not as easily flipped by an enemy compared to the directly capturable ones, because [like in the case of the asteroid], an enemy has to bomb the planet [Graveyard itself] first, except that [unlike an asteroid] the Ship Graveyard isn't eligible for a hp ("emergency infrastructure") upgrade. If the Graveyard's extractors are attacked first/directly, they also take less time to kill per unit of economic value they provide compared to an asteroid. So the Graveyard also provides an intermediate level of gameplay (between asteroid and uncolonizable [extractors]) with respect to how easy it is to lose it [and its resource extractors].
My only gripe with the Graveyard is that there isn't a Fair version of it (i.e. one with a fixed count of extractors) in the stock game, despite the fact that it's included in some of the lists with Fair in their name, but [oddly] omitted from other Fair lists, even when included in their non-Fair counterparts. For example it's included in RandomFair and RandomUncolonizable but not in RandomUncolonizableFair, which is a list type used the Small Random Fair map, typically used for 1v1, although the Graveyard can actually appear in that map via WeightedRandomFair like does in 5v5s. I guess I should mention that Ship Graveyard provides between 0-1 crystal and 1-2 metal extractors. But modding a Fair version of it is quite simple.