Group conversation box unchecked - Stock Messaging

[Phoneguy108]

Can someone pls explain how group message replies are supposed to function when you reply to a group text but uncheck the "group conversation" box. When I uncheck the box is everyone still supposed to receive my reply but just in a separate thread to them only via SMS?

 

[Phoneguy108]

the reason I ask is because when I uncheck the box I am getting mixed results on who is and who is not receiving my replies