My take on inflammation markers not being elevated is the following:

It just depends on where the inflammation is. Small amounts of inflammation in the wrong spot can cause a lot of pain. Pain sensors (nociceptors) are not equally distributed throughout the body so pain is not felt equally everywhere.

Another problem is when nerve endings become sensitized to inflammation that is chronic. It doesn't matter if it is a lot of inflammation or not. Think of a sliver that at first you don't even notice. Given time there is a small amount of inflammation and the sliver is all the brain focuses on.

I had a condition called trigeminal neuralgia. The area causing the problem was microscopic. The surgery to relieve that pain was called microvascular decompression (MVD surgery). The pain was horrific but fortunately not all the time. An MRI didn't even reveal the true nature of the problem. Fortunately the neurosurgeon knew where to look and the problem was fixed.

Sometimes trigeminal neuralgia is mistaken for GCA and vice versa but they have distinctly different causes.
https://www.mayoclinic.org/diseases-conditions/trigeminal-neuralgia/symptoms-causes/syc-20353344.