The answer to your question is it can be related to both. Because you still have one elongated styloid, I would suspect that is the culprit especially since it’s very common for the second styloid to “make itself” more “visible” via symptoms after the first styloid is removed. However, it could also be residual from the first surgery. It’s not as common a post op symptom as something like First Bite Syndrome, but it’s also not unheard of. I had burning tongue pre-op & periodically have burning tongue now, but it’s mild enough that until recently, I didn’t mentally process that I still have it.
If it’s bothersome enough, it would be worth it to pursue removal of your second styloid. If you can live with it, then skip the surgery. You can also consider taking a nerve pain medication like Gabapentin or Amitriptyline to see if that helps as burning tongue comes from the trigeminal nerve.