AVR: 5 Identical Pistons - Explained

Hello,

According to the spare parts catalog, the AVR (2.5 R5 with 80/109) has 5 identical pistons. This is unusual compared to other similar five-cylinder engines like the ANJ or APA, as it would mean that the intake and exhaust valves on the AVR would always be located on the same side. Alternatively, the valves could be recessed in the cylinder head, which would eliminate the need for valve pockets.
The replacement sets with the rings are the same again.
It is not possible to make any statements about the shape of the cavity, but the nozzles have a different part number.

Does anyone know what's being played?

"Thank you."
John.