It does look like of separated 'tabbing' caused by hull flexing, between the hull liner and the hull and the keel bolts have no rust, I will post a picture for more reference.
There is no "tabbing" or "taping" on the vessel under discussion. The liner is glued to the hull with a bonding putty. I'm not complaining about semantics, there is a substantial difference.
Taping or tabbing failure is readily apparent while the putty bonded liners have many bond areas which are simply not accessible without cutting the liner. Photo below shows a 2' X 2.5' section of liner cout out with the putty bead intact .... the liner had never made contact with the hull right from the factory. The liner was basically floating inside the hull and the entire boat was coming apart.