No ... uveitis is not the same as GCA. The visual disturbances and potential for vision loss are the same. The symptoms might be similar but an eye specialist that can do a dilated eye exam would be needed to tell what was causing the vision changes.

I don't have GCA but my rheumatologist still asks me about symptoms of GCA since I have PMR. I have every symptom of GCA but my ophthalmologist always reassures me that there is no evidence of GCA that can be seen inside my eye. Plenty of problems related to Prednisone side effects but no evidence of GCA ... my ocular nerve looks healthy at least.

This link speaks to the need for specialists when Prednisone is use as a treatment for any condition. I don't think PMR needs to be diagnosed by a specialist but treatment with Prednisone may require many specialists.
https://www.mayoclinic.org/steroids/art-20045692
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They say every cell in the body has cortisol receptors so Prednisone has far reaching effects on the body. The effects are both positive and negative so we take the good with the bad ... I suppose.

Another link that speaks to the use of steroids for ocular health.
https://www.aao.org/eyenet/article/savvy-steroid-use
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GCA is a vascular problem but it is the ocular nerve that gets damaged because of a lack of blood supply to the ocular nerve.

"Giant Cell Arteritis (GCA) can significantly affect the ocular nerve, primarily by causing inflammation in the arteries that supply blood to the optic nerve, leading to a condition called "arteritic anterior ischemic optic neuropathy (AAION)," which can result in sudden and severe vision loss in one eye due to reduced blood flow to the optic nerve."
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It is another layer of specialist but sometimes a neuro-ophthalmologist is a medical specialist who plays a key role in diagnosing and managing Giant Cell Arteritis (GCA), particularly when a patient experiences vision loss or other visual disturbances related to the condition; they are experts in identifying and treating GCA by monitoring visual function through detailed eye exams and coordinating with other specialists like rheumatologists to manage the overall disease process.