It's because the comment-engine of Wordnik comes from what was once a separate site, called Wordie, and devoted more to the social side of words than the technical side. Wordie was quite rudimentary (in the best possible way) and didn't distinguish upper from lower case. So many words which should have an upper case element are replete with old comments on their lower case form.
The Vegetable Lamb of Tartary (Latin: Agnus scythicus or Planta Tartarica Barometz) is a legendary zoophyte of central Asia, believed to grow sheep as its fruit. The sheep were connected to the plant by an umbilical cord and grazed the land around the plant. When all the plants were gone, both the plant and sheep died. (Wikipedia)