Yea but All kill is a term that existed long before instiz chart was a thing, and is in common use for many things in korea. Having top 3 on melon with your songs on melon is also known as 'all kill' for example. The most ive seen is some screenshot from instiz listing #1 on all the charts, but never have i heard news/tv shows mention instiz chart directly nor have i ever heard 'perfect all kill' or 'realtime all kill', its all just all kill.
And IU ofc care about the charts ( every artists does from what ive seen), points is, its the melon chart they care about. Every clip ive seen of IU checking the charts on IUTV ( betting with her team how her songs will charts etc), its always melon thats talked about or shown. There also some clips with Suzy from back when she released music that also shows her constantly refreshing melon chart every minute at release.