Short answer is yes the hobby has many terms screwed up
When we call classify a gene we are comparing it to the wild trait allele. Dominant means the phenotype looks the same in heterozygous and homozygous form. So a pinstripe and a super pinstripe (super being another made up term for the hobby) look the same. Spider and Pinstripe are incomplete dominant to each other and could be possibly recessive to other traits. We classify only based on the wild trait allele. Since there is no evidence of a homozygous spider, we really can't classify it. I made up the term "unproven dominant" to cover these traits with unknown homozygous forms.
That is correct. The only gene I know of that could be classified as truly co-dom is scaleless head/scaleless. Everything else as far as i can see would be inc-dom.