Agreed but think on this: if the car hasn't been inspected and approved with rails, then the manufacturer would be at risk of a hiding to nothing if anything untoward happened, no matter how unlikely. Given that situation, corporate governance kicks in. Presumable a bean counter somewhere had apoplexy.
I assume getting reapproval would be too problematic or costly for some reason so, whether or not the rails are up to the job, the path of least resistance is for the brochures and manual to be changed.
I've seen something similar in my job. There was a range of equipment approved for safety related applications up to SIL3 (suitable to help mitigate VERY serious risk of very nasty things happening). To give a low cost option, for lower risk applications, the EXACT SAME kit was certified to SIL2 (suitable to help mitigate moderate risk of slightly nasty things happening). The ONLY differences were the colour, the label and the price. Despite that, if the SIL2 approved kit got used in a SIL3 application and things went pear shaped, it would have been quite possible for someone to do jail time.