I've been a backend developer for years and at times a frontend developer.
I've applied to a few full stack positions and the amount of specific knowledge in various topics they require seems much greater than either role separately.
When hiring or interviewing we tend to build up a big list of skills so the job looks impressive and attracts talent. Don't take the requirements too seriously.
Ideally the person doing the hiring is just measuring your knowledge. But I know many interviewers just try to eliminate candidates.
I've applied to a few full stack positions and the amount of specific knowledge in various topics they require seems much greater than either role separately.