Unable to use data on eSIM whilst using the physical SIM

Question: Does anyone know why access to data on the iPhone XS eSIM is turned off whilst one is using the phone on the physical SIM?

The Issue:

1. I have an iPhone XS.
2. Both physical and eSIM have been activated
3. The eSim has my data plan
4. Whilst using the physical SIM on the primary line, access to data on the eSIM is turned off (the signal bars go to zero)
5. I am unable to surf the internet, send emails, or use data dependent apps such as maps whilst I am on the phone.

Explanations I have received so far:

1. On the first contact, the carrier's phone tech team claimed the issue was resolved but turned out to unrelated to cellular switching. Still does not work after cellular switching was turned off and on seemingly for posterity.
2. On the second contact, the carrier's phone tech team recommended I take the phone into a store
3. On the third contact, the in-store team recommended I speak with Apple as they are unaware of the issue and do not know how to resolve it
4. Wait for it...An Apple genius claimed this is a requirement of the CRTC (the Canadian equivalent to the US FCC) which "requires that the primary line have more features than the eSIM to prevent people from buying data in countries like Thailand for cheap and then using it in Canada." I could not have made that up myself. This response is both illogical and insultingly uninformed. So here I am...