Like I said -- more to do with carrier restrictions. Your carrier doesn't have Pixel 5 on the "allowed devices" whitelist, so when it sends a registration request via that eSIM the network rejects it. (Your carrier knows which phone model is attempting to activate a SIM, even a physical one, and can reject it for whatever reason. It's just less common)

My Pixel 2 supported WiFi Calling but my carrier didn't acknowledge it as "supported" and the carrier's servers refused to send it a settings file.