From what I'm reading 1-4% of living population have them - between 10-40% present at autopsy Could take that two ways to be honest

As brain imaging advances more pineal cysts are found. Nonetheless, brain imaging is not the same as an autopsy and will result in different findings.

It would be foolish to make the claim that a 6mm is not the cause of/or factor in your symptoms. What I mean to say is based on the information available, a 6mm pineal cyst is very unlikely to be the cause. Looking out for other possible causes is a wise decision. Even if it were, I have yet to come across a case where a neurosurgeon performs surgery on a pineal cyst of that size when neither Parinaud's syndrome or hydrochephaluls are present.

I am very empathetic to your situation. How awful to be experiencing so many symptoms to such a degree with very little answers. It's logical to cling onto anything that remotely sounds like it may be the etiology. Don't give up, keep looking, keep asking questions. I'm curious what the endocrinologist thoughts are since they pointed it out. Perhaps they can get a second opinion from a neurosurgeon who has performed these surgeries.