@grayway2
Flashing/installing other operating systems does not wipe installed eSIMs. For example, a previous workaround for Google Fi users was to install the eSIM while on stock, and then install GrapheneOS since it could not be set up on GOS. (That specific problem has been fixed.)
You are correct about where the eSIM is stored. GrapheneOS's duress PIN/password wipe includes eSIMs when it performs the wipe, hence my suggestion.