This is a common technique so no surprise they are similar. However, there seem to be slight differences in the way the chunk edges are made seamless.

In Trigger Rally, there are additional vertices being added to the lower LOD chunk side of the seam to avoid T-junctions in the mesh topology.

In the OP demo, the vertices on the higher LOD side of the seam are morphed so that they will be flat with the lower LOD side of the seam. This should also help reduce "snapping" when moving to higher LOD levels.