The digital ground is a little shorted to the analog ground, note that there is only one connection point. There are also different grounds on the PCB, which are determined by the system design.
When the signal line is routed on the electrical (ground) layer on a multi-layer printed board, since there are not many lines left in the signal line layer, adding more layers will cause waste and increase production. The workload and cost have also increased accordingly. In order to solve this contradiction, wiring can be considered on the electrical (ground) layer. The power plane should be considered first, followed by the ground plane. Because it is best to preserve the integrity of the formation.