Not really. The loss of heat due to the pipes being underground is probably insignificant. It all depends on the temperature of the soil surrounding the pipes, the thermal resistance of the pipes and soil, and the amount of 'heat' that is being transferred via the water in the pipes. Soil is a lousy conductor of heat especially when dry. So is ABS pipe. A simplistic explanation is this.....The heat loss (or gain if the soil is hotter than the water) due to the pipes being underground is related to the temperature of the water in the pipes versus the surrounding soil, or, the difference in temperature between the water and soil. Bigger difference means more loss or gain of heat. This loss or gain of heat would typically be a low percentage of the heat transferred between the solar and the pool because of a high flow rate. If you consider that in the near limit where flow is almost zero, then the loss or gain in the pipes would be a very high percentage of the heat transferred between solar and pool. My field heater is 90' from the pool and connected with underground ABS 1.25" pipes. Don't worry about it.
I tried to make it clear. If not, I'll gladly try again.
Al