Experience != expertise or skill. I have never met someone who was actually good at both. Maybe if your backend is just some SQL queries. I am a backend engineer and I’m adequate at front end but I’d never hire someone whose skills were merely adequate unless I thought they had the potential to reach ‘good’.
If you actually have deep knowledge in a specialty, then you describe yourself as that specialty. ‘Full stack engineer’ coneys that you don’t have a specialty/are a master of nothing/your skills are _ shaped.