"No testicular intervention" sure that could be the definition of a cactus buck in extreme cases. That's like saying autistic kids can't function because of the disorder. Fortunately there is a wide range in severity in all diseases and genetic malfunctions. Every condition can vary from a slight case to full blown cases. No different than a cactus buck. There are the ones that have a slight testicular malfunction and the ones that have no testicular function. It is still a testicular malfunction and that is what causes cryptorchids, which if you are wondering, is the scientific name for a cactus buck.
Secondly, testicles don't shrink in the spring and get larger in the fall. They are actually full grown or reach maturity at the age of 3 1/2 years old. They stay that size for the rest of their life. What does happen is, in the late winter after breeding the testicles are sucked up in the abdomen until late summer usually the first of August, at least here in Idaho. After the antlers have finished growing in mid summer the testicles are then pushed back out of the abdomen to prepare for the up coming rut. There are two main reason for this process, the first and most important is to protect the testicles from freezing and frost bite the secondly, and probably just as important to the readers on this site, is for the antler growing process.
By the way, this buck did not have all of the right equipment and did not participate in the rut.
Granted I'm not a biologist, I just spend hundreds of days a year in the field. I have video footage to prove my findings. I also do believe you can probably find it in a few more indepth reads. Maybe something by Olof Wallmo or maybe even Jim Heffilfinger.
Sorry to drag this out and yes everybody is in entitled to there opinion. I do believe that the way you see it is the most common way people view cactus bucks. This was just some food for thought. Don't take this as an argument its just the way I and many others see it.