There are threads where NERD has provided some first hand info on homozygous spider, way before your time. As I remember they said something like there had been enough spider X spider breedings without a super to prove it dominant. They seemed to discount the possibility of homozygous lethal and didn't quantify how many where "enough". When asked if they had ever proven a homozygous spider they said something like they weren’t interested enough to try. So basically just like now, not enough info yet to answer the question and end either the rumor that it's dominant or the rumor that it's lethal.

Did they say how old the pearl was?