William
If I am not mistaken, this 'spiny lok' is some sort of structure surrounding the liner. If you look from outside the liner, it looks like the liner has thread. In reality this 'thread' do not spiral upward or downward.
During casting, the 'spiny' will interlock with aluminum to ensure better contact if compared to liner without any 'spiny'. It is also very important as the molten aluminum solidifies as the 'spiny' and the aluminum will be in stress and holds together tightly.
The 'spiny' also works by increasing the surface area in contact between the aluminum and the cast iron liner. The maximum surface area in contact will also ensure that the heat transfer from the bore surface to the outside of the liner and to the aluminum will be maximized.
I have seen liner that has vertical grooves, rough surface (looks like it has just been grit blasted), etc. There are many type of liners available. The idea of using this 'spiny lok' is not new as it has been around in various Japanese and European cars.