We’re suffering from historical usage becoming increasingly wrong over time.
Firmware generally refers to low-level code burned into a device’s ROM (or more commonly today, flash). For small embedded devices like appliances, it contains all of the device’s software. For bigger things like computers, it usually refers to things like the BIOS/EFI/BootROM code - software that is not stored on primary storage (hard drive, SSD, etc.)
For mobile phones, the term used to be perfectly appropriate because the original mobile phones were fixed-function. They supported phone calls, texting and maybe a few basic built-in apps, but nothing else. So firmware was an appropriate term. When mobile phones started supporting apps (so-called “feature” phones), there was a distinction between the apps and the firmware (which was everything else).
But a modern smart phones and tablets are far more like computers than appliances. There is a low-level set of pre-boot software that initializes hardware, authenticates the OS and then boots the OS. Most people would call that code “firmware”. But the OS itself and the apps bundled with the OS really aren’t - no more than macOS and its bundled apps are firmware on a Mac. But phone manufacturers (not just Apple) continue to call it firmware, because that’s the term that was used back when mobile phones were far simpler devices.