I've investigated the setting "Single view for multi-opened files" a bit more, please find a summary in topic "0.83: Behaviour of "Single view for multi-opened files"
From what I can see in XnView Classic this setting is supposed to affect the Start-up and Drag&Drop to XnView in View mode, only. The current translation in XnView Classic describes pretty much what this setting does:
"Open only one view for multiple files (startup & drag-drop)".
The addition "(Startup & Drag&Drop)" is very essential, so I'd suggest to rename the setting to "Startup & Drag&Drop: Open only one view for multiple files"
Instead of "view" we discussed using the term "tab", but "view" is the term used for an image opened in XnView in a tab for viewing. And the setting category is named "View". So I'd stick to the term "View".