Well sadly, I think the original idea for the B.o.S. was to have them hear you and not see you, but based on the actual gameplay, they definitely used some sort of "sight" to notice you. Sadly, the hearing feature was probably too difficult to implement and had to be cut.



So while it's kind of weird to have an essentially blind character use sight to notice you, I think it was probably a good idea to use those signs as a way to let the player know how it was all going to work.