This is somewhat of a misconception. The variants they test for change over time as new biologically significant SNPs and haplotypes are discovered.
One of the things that is a little misleading about how they present results is that a "negative" result means they don't know (i.e. not one of the SNPs they test for) rather than you have a "normal" copy of some particular gene.
One of the things that is a little misleading about how they present results is that a "negative" result means they don't know (i.e. not one of the SNPs they test for) rather than you have a "normal" copy of some particular gene.