Not supported, because we’re never told that the cultural conservatism of Spanish allows for a “stable, reliable” form of expression. The author doesn’t indicate that cultural conservatism plays any role in the alleged reliability of Spanish as a form of expression.

“Only recently” is not supported. We don’t know whether this practice of incorporating elements of other languages has occurred only recently or whether it began much longer ago.

Supported. We know from the beginning of P2 that Spanish poetry has a less critical attitude toward the Spanish language than Latin American poetry does. This leads Spanish poets to take “their language for granted.” We also know from P3 that Spanish poetry displays cultural conservatism that leads it to romanticize its past. It’s fair to consider the less critical attitude of Spanish poets toward Spanish as an example of the way in which Spanish poetry is culturally conservative. It’s less willing to experiment with language and explore other poetic structures.

We’re never told that Latin American poets use “Japanese words and phrases.” They may use poetic structures from Japan (haiku), but this doesn’t imply the use of Japanese words and phrases.

There’s no evidence Spanish poetry is accepting of the influence of Spanish-language poets outside of Spain. We have no evidence that Spanish poetry is receptive to outside influences.