Crystal Oscillators have two leads, there is no polarity for crystals and hence can be connected in both directions.

Does Xtal have polarity?

Do the crystals have polarity? No. In EXTAL and XTAL, which is input and which is output pins? As explained in that appnote and shown on the diagram, EXTAL is an input and XTAL is an output.

Do crystal resonators have polarity?

Polarization on ceramic resonators: Both quartz crystals and ceramic resonators do not have polarity since leads can be mounted interchangeably.