Not true. With some idealization, the shrapnel forms a cylinder expanding in radius and height. It's neither disk
A thin cylinder (that is with the height much lesser than it's radius) is usually
called a disk.
The cone is an area formed by that expanding disk during the event. All
objects within that area would be hit by striking elements.
Anyway, the surface area is many hundreds of sq. m. depending on the distance from the explosion to the plane.
The @blackbird69's post i answered was about the small size of the damage
area. 'Many hundreds of sq. m.' would produce a much larger area of holes in
the fuselage.
Shrapnel density is not high.
It depends on the ratio of the average speed of striking elements to the difference between the speeds of the missile and it's target.
If the speed difference is much lesser than the average speed of HE (as in
the case of a MANPAD hitting into the aircraft's tail) then holes would be
densely distributed throughout a relatively small area. If the speed difference
is close to the average speed of HE (that is the case of MH17) then the hit
area would be greater and less dense of holes.
Anyway holes must be evenly distributed throughout the damage area, not
the patches of holes as on the deck's floor.