About eSIM on iPhone - Apple Support
"You can install eight or more eSIMs on an iPhone and use two phone numbers at the same time."
Using Dual SIM with an eSIM - Apple Support
"All iPhone models that support eSIM can have multiple eSIMs and use Dual SIM with two active SIMs at the same time.
You can use Dual SIM by using a physical SIM and an eSIM. iPhone 13 models and later also support two active eSIMs. iPhone models without a physical SIM tray support two active eSIMs." (emphasis mine)
I could be mistaken, but I am taking this to mean that an iPhone 13 series phone can have two active eSIMs if it is a variant that supports eSIMs, and no physical SIM is installed. It does not sound like an iPhone 12 series phone with a physical SIM tray, and the ability to use eSIMs, would offer the "two active eSIM" option.
You might want to look at some of the links in the first Support article, like this one:
If you can't set up an eSIM on your iPhone - Apple Support