That is not entirely accurate as far as I understand from a friend who farms different crops. He said he has the choice between tilling a field to get rid of weeds and spraying it. Glyphosate is active on the living plants on that field, so all weeds die (as they would if he were tilling), but the soil remains fertile as it is not dug up and dried out. A week after spraying, the effect is gone and he can start planting.

Special hybrid crops with glyphosate resistance are expensive because they increase the yield and enable you to spray pests while the crop is growing without killing the crop. You might as well plant conventional seeds after spraying glyphosate, but you can’t fight weeds with glyphosate after you have planted.