I’d return to your endodontist to ask if the bone graft will settle down over time as it heals, or if it will need further shaping in preparation for the dental implant. While it is important for there to be sufficient bone for your dental implant, the shape of the bone and the gum tissue also affects the aesthetic outcome of treatment and whether the implant tooth feels comfortable and is easy to keep clean. If you are not happy with your endodontist’s explanation, definitely seek a second opinion.