Three piece headlining kit??

So I ordered a headliner kit (67-72 5-bow Dodge Dart) from Year One recently expecting a simple five-bow headlining kit, which should be just the headlining by itself.

But a three piece kit arrives.

The main top section doesn't seem to have extra material for the c-pillars, but instead it has a pair of thin cards that are trimmed in the same perforated material (I've included a photo).

Is this normal, or am I freaking out about nothing?