Grouping when Streaming via BT or Airplay with WiFi but no Internet?

Basis the article below I understand that while using the mentioned devices I can stream via BT and group other speakers via WiFi.   

We have a 12 zone system in our home and have for years.   We are very happy with the system and understand it’s functionality.   We’d like to add a small system to our camper, three speakers.   100% of the time we have a WiFi available in our camper.  Based on where we are about 75% of the time the WiFi network is connected to the internet and 25% of the time it’s not.   I understand that during the 75% of the time we have WiFi and Internet the system will work just as it does at home.   What I would like to understand is during the 25% of the time we have WiFi but no internet would we still be able to stream via BT to one of the devices mentioned on the linked article and group with the other two speakers?

https://support.sonos.com/en/article/share-roam-s-bluetooth-audio-with-your-sonos-system?fbclid=IwAR1S0DSrv71AwlbBnPqwo1nDvbutG2guLxPVQac62KyT7nnrkECCGyyzyfA