NIC question

I came across a question but many have asked the same question in the forum before.
It was about mileage allowance related to NIC.

So it was answered that the mileage allowance is 45p when it comes to NIC. The cut off point for 10000 miles doesn’t apply to NIC.

The question was asking about employer’s Class 1 NIC.

So the answer took both the employee’s salary plus the excess mileage allowance received.

My doubt here about the addintion of excess mileage allowance received. Is it because we consider it as a cash remuneration?

Thank you.