Default 'singular' lookup for $tc() pluralization is not working per API docs

[GregPeden]

vue & vue-i18n version

vue 2.3.3
vue-i18n 6.1.3

Reproduction Link

https://jsfiddle.net/gregpeden/w5t1e619/

Steps to reproduce

• Provide any localization definition prepared for pluralization
  • Example: 'address` => 'Address | Addresses'
• Reference the pluralized definition using $tc() but without including the quantity (Which should imply a signular lookup per docs)
  • Example: $tc('example.address')

What is Expected?

Per API docs, when using $tc() for localization, the default value for pluralization is 1, implying that the "singular" lookup will be returned
https://kazupon.github.io/vue-i18n/en/api.html

What is actually happening?

The entire localization string is returned including the pipe character:
Example: Address | Addresses