The eSIMs in phones are reprogrammable with new “profiles”, and Android can store multiple profiles and reprogram the eSIM with whichever one you want to use. Non-programmable eSIMs are only used in embedded devices.

Android 13 also has something called eSIM MEP that allows it to do dual SIM using a single eSIM chip.

Edit: here’s Android documentation for developers on eSIM MEP: https://source.android.com/docs/core/connect/esim-mep