When soil is hard and compacted it prevents the fine delicate roots from growing and moving in the soil. One consequence of this is that the plant puts a lot of energy into growing big roots that try to push through the compacted soil. This means that the plant will struggle and not grow as big above ground as it is using most of its energy in below ground growth. The ideal scenario is a light and less compacted soil that encourages the abundant growth of fine roots. The more fine roots that develop and the easier they can move through the soil, the better the nutrient and moisture uptake. The plant will then focus on growth above ground.
Both plants in the photo are the same age. The plant on the left is growing in RINNAL.