True. But he did say there was a catastrophic miscalculation on his part which caused a fire on sector-B, which coused the stabilisation feild of the Laboratory to fail because of a fire after his masters (Ancients) started combusting. But we shall see what the future holds
Tinkerer said that Demons (& Angels) take on different traits depending on the Deity they serve. Nergal's all look like stereotypical Biblical Devils/Demons (Succubu & Imps). He has mentioned that Angels who serve Qetesh would most likley be themed more around Greco & Egyptian-like creatures.
The 'generic' look of the Lesser & Greater Demons is more to do with their unaffiliated nature. They dont have a god they serve. Also Greater Demons look like juiced-up Xenomorphs lol