Neither of the "Disable foo" checkboxes in Edit->Preferences->Advanced->Menubar Access seem to affect the Shift+Ctrl+W hotkey; nor do the "MiscTabCloseFoo" entries in terminalrc.  And unfortunately Shift+Ctrl+W is one pinky slip away from Ctrl-W, a common hotkey (bash, vim, etc).

As a workaround I enabled editable keyboard shortcuts globally, then changed close-tab to Alt+Shift+Ctrl+W to get something that isn't accidentally typeable, but being able to turn off tab insta-kill entirely via an easier to find option would be nice.