1. it's possible that the author is blind in a legal sense but not completely blind -- e.g. maybe they only have vision in the center of their visual field, or maybe they have low acuity. You'll often see people with white canes wearing glasses, which would be pointless if they had absolutely zero vision.

2. It's not uncommon for people to use terms like "watch", "see", "hear", "listen", etc. colloquially / metaphorically; e.g. "I heard that X did Y" by someone who, pedantically speaking, _read_ that X did Y; someone typing "listen to me" on a chat app when they really mean "please read my words carefully and internalize them"; etc. If I were playing a video on on my phone, listening to what is being said but not actually watching the screen, I'd probably still say I "watched" the video.