User blog comment:Xilinoc/Ch. 581 - THE HERO 2/@comment-24153155-20140521225952/@comment-24282510-20140522005349

Besides what Spacecornet said. Remember that the Sternitter spread reiatsu all over (whereever they are right now i don't recall the name). This mainly was to hide their movements so the Gotei 13 could not sense them but it likely is making it hard for the Gotei 13 to sense other members of the 13 besides the really strong ones.