hence why organics are only found on rare habitable worlds
Organics are supposed to be more plentiful in toxic worlds, worlds like Salamanca are sought after for their organics extraction.
They occasionally exist in large quantities in toxic worlds, but this is the exception, not the rule.
The main source is habitable worlds, like how the hegemony gets the bulk of theirs from Jangala's Xenolife.
I always saw organics terraforming as you injecting some compounds into biological matter deposits to accelarate the formation of oil and coal, or stuff like that.
Still, there seems to be a correlation (at least in vanilla core worlds, not considering randomly generated worlds) between availability of organics and the danger it presents. Jangala and Salamanca are the two bigger sources of the resource and both of these present a type of additional hazard, Salamanca being obvious and Jangala while being habitable, it is hardly a safe place to be given it's conditions and xenolife.
Meanwhile, the tamer worlds, like Gilead, Tartessus or Volturn, they have a not insignificantly lower production of organics, maybe due to climate (colder worlds like Eochu Bres barely has any organics at all) or maybe because their focus is on food production. Random worlds don't seem to follow these conditions, so it is possible that plentiful organics can just grow on any habitable planet consequence-free, but the core worlds at least seem to indicate that max organic production come with an inherit risk.