Question WiFi call using SIM card 2 - Google Pixel 6

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I have two SIM cards in my S21 that allows me to call to Brazil using WiFi without have to start the number with country code. It works perfectly in such way that I never imagined. On Pixel 6 this is not available. What is required to the phone to work like that? I thought that any 5G should have the same features. P6 says that can do WiFi calls but not like S21!

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I've been trying to figure out a way myself for months.
The setting is called Backup Calling (Samsung calls it Auto_Data_Switching).
Anyways, it doesn't seem to be as straight forward on the Pixel devices. The switch for backup calling has only showed up for me on the Physical SIM. Also, its only when I turn the switch for the sim off and then on again; it disappears super quickly and I don't understand why. I should add that when I turn the sim back on, I have to scroll super quickly to the bottom, select which line I want data on when the notification comes up, then quickly switch backup calling on before it's gone and replaced with Wi-Fi Calling. Sometimes it stays but I don't think it does anything as something system wise is not enabling it.
But it's really the eSIM I want this on because I have data on the physical SIM only. So to have Wi-Fi Calling over cellular data via SIM 1 would be a huge relief. But the switch for backup calling doesn't show up like it does on the physical SIM. Scrolling to the bottom trick doesn't work as the notification is different (something about calls and texts switching to the eSIM).
I think "Cross SIM Calling" and whatever related to it is what we need to look at.

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Let me give you more details. My SIM card 2 is roaming and both are phisical. When I have to call to Brasil using at&t SIM 1 or SIM 2 roaming, I have to include +55 11 if I am calling to São Paulo but; because the SIM 2 is from São Paulo; when I am calling using WiFi to SP I don't use +55 11 and the VIVO network register my call as local inside their network. I can call numbers like *555 for voice mail; something impossible if you are in roaming. This huge benefit come from S21 + WiFi call; not available on P6, unfortunately. I have a brand new P6 in my bookshelf because I figured out S21 is far better than P6.