I don't think that the issue is so much with the ability of a product to make a good, long lasting connection that could be covered and work well for the life of the building and other wiring when properly installed, I think it's the inability to check the quality of the installers work after said splice is buried. Once a device like this is allowed on the market, anybody will be able to get them, and we've all seen the horror of DIYers in action. A badly made splice out of the confines of a box is a fire waiting to happen.
