Bro if this is bad engineering then almost all thhe automobile engineers aare less qualified thann you are
I gave the example of Honda's D-series engine so that you could understand what I was saying. If the block and head are designed to be 1.8 ltr, then putting smaller pistons and reducing the bore would not hurt it. Understood? What it means is, that the G13 was not designed to be a 1.3 Ltr engine only when designed. In pakistan and some other countries, it was sold with this displacement. However, it was sold with bigger displacements as well as it was designed to be that way.
Peace!