I would not consider this type of piping as buried piping in the stress analysis. The thermal conditions are not given. In case the thermal load exist the side way restraining effect of the soil is not reliable or available. I guest this type of cover is used against the sun exposure by using the soil thermal conductivity.

The pipe will expand under the thermal load, the load will push the soil at around the elbows or turns with large radius, therefore the soil will not restrain the pipe at all.
Additionally the compaction cannot be guarantied since there is no sufficient side restraint of the soil. This will not provide the required axial restraint of the soil.
The top soil with this arrangement can be assumed as uniform load but this is not conservative at around the elbows/turns lateral and horizontal since the stay of the soil cannot be guarantied for the pipe uplift at elbows.

If I was the decision maker on the job and the pipe burial is too difficult and costly, I would provide bottom supports/guides for the pipe to be able to control pipe thermal/seismic behaviour, and still provide the soil cover similarly against sun radiation (if this is the concern) on the pipe steel if it is cheaper and safer than conventional hot insulation.

Hope it helps