We absolutely continue to respect that check box. We won't always check at startup if Firefox is your default browser. When that box is left checked, you get a modal/prompt at every single startup. It literally always checks if Firefox is your default.
In contrast, the work resulting from this bug is just checking every 5 weeks and we happen to not be default, we'll ask with a more gentle infobar. We won't display the more disruptive modal/prompt.
I love Firefox, just stop shooting yourself in the foot. There is no way that is a fair interpretation of that option.