Aircraft structural aluminum alloys are heat treated/aged metal.
If the wing box was heated excessively, the metal could lose strength without being holed.
The fuel on the other side of the panels acts to absorb heat from the metal and initially will limit the temperature rise, but when the fuel gets hot enough, there may be a loss of heat transfer as boiling of fuel begins and the metal can then begin to cook.
They will probably do hardness tests of the wing skin to evaluate its strength in the heat affected areas.