Wrong! The fact that it is a genetic problem makes it a very real health concern. Any birth defect can and should be. My spiders and spider combos do not have any symptoms, not one, at any time and neither do any of their offspring. When I purchased my initial spider and yellow belly spider I was extremely careful to be sure that they had zero wobble, stargazing, head rolling, etc..
For starters, it is much less appealing to customers to buy a defective animal and yes, no matter what your opinion, the neurological defecits displayed are very much a defect and any animals with them are considered "B" grade in the market automatically.
When you breed animals that have obvious genetic flaws don't you expect to get babies that have it also? If you line breed or even just breed back partially related animals you run the risk of producing animals that have difficulty eating, look to the uninformed consumer like they have IBD or some similar affliction, and potentialy it leads to even bigger problems.
Do we know how much worse it can get or what else it can lead to? Not many spider x spider clutches out there. Most people have bred them to other genes to make combos so we have not seen the worst of it. The fact that there is no visual super spider is a blessing too in that has prevented more related, defective spiders being bred to each other.