Likely due to the intrigue, darkness and mysteriousness behind so many rumors and myths of the number 13; at least, that's my conjecture. Though, the program I designed still continues work on domestication and weaponizing attempts; utilizing cell cultures they modify and splice with the more successful experiments. Unfortunately, they were set back by my own quaternary 'sona, Ares (a Deinosuchus Android, his organic body once that of a soldier in the US military, made into the ultimate weapon of war), when he laid waste to a good portion of the facility trying to escape the hell he was forced to endure there.
Bio-weaponry creation, in all cases, is a very difficult and problematic effort. So much of it relies on the luck of the draw with genetic recombination and alteration in an attempt to find that distinct perfection; and we all know perfection is fleeting. 13 is a good... err, Alien, though. He only wanted to escape termination; he should be so glad he won't become a Queen, like you stated in your post in "What would you do if, one day, you woke up as your fursona?" That much was a success, at least.