That is good customer service! Makes me feel better about purchasing them for my son. Only considering the 12k ramps from AAP (~$42), though.
As for the metal ramps sliding, once I added the low profile extenders that became a less of an issue. Once the weight hit the extenders, it sets the metal ramps. When they did slide, they just slid forward(slick garage floor), as described regarding the rhinos. Never had an issue with driving off the end, imo that would be ignorance no matter the type ramp. That said, always good to have two people (driver/guide) involved when driving up ramps, but with care, not a necessity.