My headcanon is that the people outside the classroom aren't there for just Saeki, but that they're well aware of the sleeping volcano of a romance... And they're hoping to catch a glimpse of some indications of ... Seismic activity?
if you go back on the many past images, there are many parodies of the spider-kabedon on here. my favorite is Tohru spider-kabedoning on Kobayashi which mirrors this image.