The most common reason for these scratches is if the contractor has started to abrade too soon. At this stage, the surface of the finish is still slightly sticky. Most of the water has evaporated, but the coalescing agents are still evaporating. These evaporate quite slowly, so if you start to abrade the floor now, there is a good chance that the finish will fasten on the abrasive and scratch the surface.
A good way to check if the finish is dry enough to abrade is to touch the finish with the back of your hand. if it feels cold on the surface, then drying is still in progress and you will have to wait a little longer. If you open a window to create better air circulation, you will speed up the drying process.
Practical tip: let the finish dry properly before abrading