What does "all day" even mean? It's marketing slop. All work day? All waking hours day? All 24 hour day day?
An Apple release gives you a number of hours and they tell you roughly how they measured it. This just says "trust me it's good." This isn't to praise Apple, it's just the bare minimum.
So vibes battery life. I'm going to assume it's like most Windows laptops and somehow only lasts 3 hours.