Counterpoint: this isn't Draketooth's Dungeon, even in Draketooth's Dungeon nobody could see them until Haley pointed them out, and regardless, different traps don't have to function similarly. Just because the audience gets to see the traps as a visual guide by the author does not mean characters csn see them, just as we saw invisibly Vaarsuvius in Xykon's tower, but Xykon couldn't see them.
If the characters act like they can't see the trap, you should probably believe them.