I think there is a misunderstanding on the api -> popup-> events section.
In details at @open and @close description it seems the text refers to marker rather the popup.
@open
Description: Fires when marker added on the map.
Payload { popup: Popup } Object with MapboxGL Popup object
#@close
Description: Fires when marker added on the map.
Payload { popup: Popup } Object with MapboxGL Popup object
https://soal.github.io/vue-mapbox/api/popup.html#events
I think there is a misunderstanding on the api -> popup-> events section. In details at @open and @close description it seems the text refers to marker rather the popup.