But my point is that presuming spider or any other mutation without a proven homozygous version isn't homozygous lethal is taking the same liberties.

Unless you get apparent homozygous animals that all die like the HG woma it’s very hard to prove a homozygous lethal . The much easier thing would be to prove that they aren’t homozygous lethal by proving a homozygous spider. But 21 years into the spider project still no public homozygous so who knows.