iPhone deleting from two exchange accounts at once when CC'd to both

I have repeated this on multiple iPhones with multiple different completely unrelated Microsoft Exchange accounts (even with each account being on a different Microsoft 365 Tenant).

My iphone specifically is an iPhone 14 Pro running iOS 17.4.1

I have multiple Exchange accounts on my iPhone, on different 365 Tenants. For the sake of discussion we'll call them Exchange Account A and Exchange Account B. If an email comes in to Exchange Account A, but it is CC'd to Exchange account B, I can delete the message in either account, and it will be deleted on both exchange servers. This is only part of the problem.

If I hit "reply" from the message in Exchange Account A, it will send the reply FROM Exchange account B. If I hit Reply ALL on the message in Exchange Account A, it will send the reply FROM Exchange Account B and CC Exchange Account A.

It seems as if it is treating the messages as if they are 1. This should not be possible, especially the deleting from both accounts. I have repeated this on different iPhones, tried deleting the accounts, restarting the iPhones, and re-adding the accounts even in a different order, and still the results are the same. This also does not seem to be impacted by the "default" accounts set on the phones.