Something wierd with mac address' that I cant explain on my i2600 Series F5 LTM HA

We have 2 F5 LTM i2600 series physical devices running v13.1.3.2. We have 4 X 1G interfaces and 2 X 10GBFiber interfaces. One of the 1GB interfaces is patched and is used for the Management IP. Both 10GBFiber interfaces are patched and used for our Internal and External vlan.

The weird thing I cant explain is why my Internal & External Vlans are using the mac address of 2 of the 1GB ports that are not patched, respectively.  FYI..These F5s have been in use for 18 months without issues.  I attached a screenshot.

The only reason I noticed this is because we were adding a VPN in our environment and were tracing the traffic from the F5 during troubleshooting. The networking team was seeing a mac address that I told them couldn't be because the port was not patched. When I started looking deeper, I found that they were right.

So my question is why is the F5 using a mac address belonging to a disconnected Interface for another connected interface that has its own mac address? Can anyone explain this behavior.