SDI pistons without steel ring carriers (!)

Hello,

I just disassembled a 1.9 SDI (ASY) engine, and while cleaning the pistons, I noticed that they don't even have a steel ring carrier for the top piston ring .

The pistons are from Nüral, instead of Mahle, and they have a slightly narrower design (where the piston skirt contacts the cylinder wall), and they also seem lighter than comparable TDI pistons (ALH, ASV).
However, ASV already has oil spray nozzles for the piston bottom cooling, but not sputter bearings.