We're not doctors here, so not experts.... Have you been given a measurement for your styloids? It's just that different doctors use a different 'average length' to decide whether they're long or not. The average most doctors use is 2.5-3cms, but some doctors say they don't consider styloids to be long unless they're over 4 cms! Some members on here have had problems with styloid processes of 2.5-3cms, and even shorter, it depends on the angle as well. Yours look on the long side, to be reaching past the C1 process, and are both quite angled at the ends.
The one side I've had removed was 4.8 cms, but the doctor said that it was compressing the jugular vein along most of it's length, he had to take it off at the skull base to remove all the compression, so I presume it would've caused a problem however long it was. The fact that yours can be seen by your vascular neurosurgeon to be compressing the IJV would be enough for me to decide to have surgery. It is such a tight space in that area, with many of the cranial nerves exiting the skull, plus the major blood vessels, that even a small shift, such as would've happened with your fusion surgery, could be enough to bring the styloids into contact with something important!!
Hope that Dr Cognetti can help you!