With alusil engines, honing the bore to bring the silica molecules to the surface is a must. However, that's for long term durability. The silica impregnated aluminum is very durable but they still need a coated piston to use in the bore. Mahle pistons for use in a alusil engine are coated. They use pistons that are coated with iron. Directly from the Mahle website:

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For the application in aluminum cylinder surfaces, MAHLE uses its own development, the iron coating FERROSTAN®, or the iron particle reinforced synthetic resin coating FERROPRINT®. These coatings are necessary to enable the combination of aluminum pistons with pure aluminum engine blocks and hence represent an essential contribution to an overall reduction in engine weight.