LATAM is at it again...unless something really has changed.
On the Chile website, when booking the cheapest fare for SCL-PUQ, this message pops up before you choose seats and pay:
La tarifa que seleccionaste es exclusiva para residentes.
El dÍa de tu vuelo tendrás que acreditar esta condición en nuestros mostradores o se te podrÍa cobrar una multa.
Reviewing the rules for these A and G fares, I see nothing about these being resident-only.