Why is it recommended to carry out spring pruning of plants before the start of sap flow?

Pruning of plants is usually carried out in early spring before the start of sap flow, in order to damage the plant less. At this time, it is still at rest. Trees and shrubs are cut. If pruning is carried out later, the plant will be depleted from the leakage of juice through the saw cut and it may even die. Why? After a period of rest, a period of active growth begins and mineral substances from the root begin to rise through the vessels to other organs of the plant. These minerals are needed for the growth and development of the plant during the growing season.