Disclaimer: I'm not working in BIOS/UEFI.
But with 25 years as developer, I would say: it depends. Mostly on the size of the company. Big companies are bureaucracy machines. You will be most of the time filling reports, doing documentation, safety assessments, requirement management etc. And less than 20% actual coding.
In small companies you will be doing 80%. For BIOS/UEFI I can imagine machine code work.
From the question I estimate that it would be good for you to apply. For sure you will learn a lot of interesting stuff, that will help you to do better SW when you work in upper levels of abstraction.