Sending an email via API for a sub-account template results in a false positive

[eeikbon]

Summary
We have a main account and several sub-accounts. We have an API key for the main account and each sub-account and templates are associated with the sub-accounts. If an API send request is sent for a sub-account template with a sub-account API key, it returns 202 and is sent successfully.
If an API send request is sent for a sub-account template with the main API key, it returns 202 but the email is never sent.

Expected
It was expected that using the main API key would result in a negative response, not a positive one