Sam,
Another possible reason for EJ on pump suction might be settlement of the tank foundation, causing initial displacement of the suction piping to pump.
This would not be a thermal expansion load with multiple cycles. It would have added loads to consider on a pump.
Since pump suction pipng is usually of larger diameter, and installation requirements might dictate straight run inlet piping to the pump suction, there could be more challenges to designing adequate flexibility into pump suction piping. Pump discharge pipipng has fewer constraints. The discharge pressure also has more concerns for EJ thrust loads, leaks, or failures.