The spider trap encounter had testing data leftover so it will appear most of the time in the current release.
There are steps in the customization process where the game regenerates the player, specifically if you change the race, sex, or age or back up from that step. When the person is regenerated you will get new genetics. That said, the bonus for 100% fox is +2 agility. Apparently there is some crude genetics work happening at the end of the customization process that always forces the player and starting slave to be purebloods and the player's racial bonuses are not updated afterwards.