Can't speak for most firms, but I interned at Jane Street and this definitely wasn't the case: almost everyone there worked 45 hours/week with a consistent schedule (market hours + a small buffer).

It makes sense: they value people doing high-quality work and avoiding mistakes. Everybody there was also clearly very productive—it was one of my first experiences that convinced me that long hours are actively counterproductive.

I understand other firms in the space (like Citadel) have pretty different cultures, so it's not going to be true for the entire field.