I'm full-stack, as they say, but have been working almost exclusively on the back-end for the last couple of years. I don't think I remember a time when I did something in the front-end that resulted in it working in Firefox but not on Chrome, so you might be right, but I may also simply not remember.
Edit: if any frontend/web developers today reads this, please do use Firefox for development. I'll tell you why:
I can only remember a single time that I wrote something in Firefox that didn't also work in the latest IE, Chrome and Edge.
Web developers I work with who use Chrome however seems to constantly have to go back and fix stuff that doesn't work anywhere but Chrome, exactly like web developers who developed in Frontpage and IE had to.
If you don't want to spend time with regressions from QA and you don't want to look unprofessional, develop on Firefox.
The happy feeling you get from doing something good for the web is a bonus.