It isn't really about damage to the runway, all runway inspections routinely look for that.
It is more to do with procedures required to hold an aerodrome licence, following any incident, a runway inspection is required; they look for anything which may have come from the aircraft, not specific to this case but things such as engine parts for a catastrophic failure, tyre damage, fluids like oil or hydraulics, brake damage (in some of the older style brake units the pad material can look more like expanded foam following a high speed reject) nuts, bolts, panels, fairings, stuff from fire engines which attended the incident. and the list goes on.
Once the inspection proves the runway meets normal criteria it may be used again.
With regards to the overweight landing, the aircraft manufacturer or operator will have provided the crew with information and training to limit damage and engineering inspections to a minimum. Whether it was prudent to carry it out or delay until MLM will no doubt be the subject of debate.