I think their comment has two parts.

First, they're saying that this is a longstanding trope in mythology and literature, the character who can see the future but isn't believed, like Cassandra. Lord of the Rings isn't my thing, but I assume they're giving examples from there as well. Dune is kind of a digression, in that those characters could see the future by recognizing how patterns were going to play out, but there wasn't any element of not being believed.

Second, they're talking about being neurodivergent themselves, and having experienced this kind of pattern recognition prediction thing. They're saying that once someone caught this on video. It's not clear exactly what they predicted, but apparently, looking at the video, it's still obvious to them what the cues were that they observed and used to predict whatever it was. I guess the people around them didn't see it, and were mystified about how they knew to do whatever it was they did in response. They think that the others should be able to look closely at the video of the incident, maybe zoom in and play it at reduced speed, and understand how they recognized what was going to happen, because they could point out all these cues; but they're frustrated to know that won't happen. Subjectively they experience the situation as though it lasts much longer than it does in the video, as though time slows down, which they tried to explain by using video game references.