Idk why the fuck they decided to put that lame ass 'joke' , but it refers to Instagram.
Authors don't use the real word out of fear for copyright, im pretty sure. Most the time the Author will chose their own word like blexgram or something as basic as thegram, and translators will change it.
If I'm wrong about the copy right thing, my bad, all I know is they don't use the real word to social medias, I've even seen it with YouTube, they use wetube of thetube.
You are indeed right, it's for copyright reasons. That's why in anime it's always Wacdonalds in stead of McDonald's
Wtf is a skibidigram?