Good day, Rex. It was of great help, actually. So, if possible, let me consider your comment as the best answer, and thank you again as well.

Hello! Both uses have the same meaning. You could basically take the phrase to mean this, "If nothing else were true, it would still be the case that". To use your examples: "If nothing else were true, it would still be the case that you have to work even harder when your dad's the boss." and "I think I'm pretty honest about my emotions most of the time; If nothing else were true, it would still be the case that I'm too frank about them [my emotions]." Does this answer your question?