with a bulkhead haven't changed in thousands of years. The material may change but the methods don't because they work. What my father did 40 years ago is as valid now as it was then or as valid as what they did in the 1400s.
As far as the contractor's repairs, I can't say without seeing their work, but making external repairs to a rotted out retaining wall is generally foolish. The soil coming through the worm eaten wall is going to put a tremendous amount of pressure on the 'fix' and when the fix fails it's going to be dramatic. Nothing is going to stop the rotting of the original wall and any exterior fixes are only hiding the problem. The repairs need to be done from the interior side which requires digging out the fill behind the wall, replacing the rotted wood, and installing proper drainage and supports so the weight of the soil helps hold the wall together. Think of the wall as a dam on a river, which it basically is. A dam is designed to have the water pressure help hold everything together. If it cracks, the repairs are done on the upstream side, not the face of the dam. Any repairs on the face will be blown out by the water pressure. The exact same principles apply to the bulkheads except we are dealing with wet soil, which has a lot more pressure behind it.
Building and repairing seawalls is not something to be tackled by those without the proper training and knowledge.