It appears that this bug has been present ever since the functionality to specifically ask about horses as farm-business assets was introduced with 2013 TurboTax. All versions of TurboTax from 2013 on have the same behavior with regard to this. Prior to 2013 TurboTax, one had to make the entry as Other and manually enter the asset class and recovery period.
Breeding or work horses more than 12 years old when placed in service are also handled incorrectly. These are 3-year assets with a 3-year recovery period, but TurboTax also incorrectly produces a 10-year recovery period for these.
