Under a Dark Angel's Eye

product.has_only_default_variant: true
product.options_with_values.size == 1: 1
product.available == false: false
block.settings.unavailable_variants == 'hide': show
target.option1: Default Title
product.option1:
product.options_with_values: [{"name":"Title","position":1,"values":["Default Title"]}]
product group:
product type: Book
is_new_or_remainder_or_default_title? true
has_only_one_condition_option? true