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Could this ratio reality be akin to male tri-colored cats being so rare and frail?
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Calico is caused by a female being heterozygous for coat color alleles on her X chromosomes. Because of random X inactivation, each cell of the female only expresses one allele or the other, resulting in calico colors. Males have one X that is active all the time, so they cannot be heterozygous for the coat color alleles that cause calico, unless they have the configuration XXY instead of XY (the presence of two X chromosomes during development automatically triggers random X inactivation). In humans, XXY is called Klinefelter's syndrome and results in sterility and other issues.
I can't think of many plausible mechanisms that would prevent homozygous tesseras from being produced in the expected ratios if there isn't embryonic lethality, unless they involve prezygotic mechanisms (like for some reason a sperm carrying the tessera allele can't bind well to an egg carrying the tessera allele, such that the tessera egg almost always gets fertilized by non-tessera sperm instead...but this seems far-fetched). I guess someone needs to do a more rigorous analysis by holding back all the tessera offspring of tess x tess crosses.
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