It's clear that the humans in the terminals are not directly associated with the Forerunner civilization, but why they fascinate Librarian is unknown. Some speculation argued they might be a different species, some speculation argued at the time that it only made sense if it was a different group from the same species (whose existence surprised the Librarian and led her to wonder about the Forerunner civilization's identity).

: Then there are the human styled ruins on the Delta
: Halo

So?

: the control panels designed for the non human hands which.

Lol? The control panels hardly seem designed for anything in particular. They're like everything else; silly abstract futuristic mumbo-jumbo.

: Arbiter: What happened to the forerunner?
: Spark: They died as planned.

So?

The H==F argument doesn't rely on the Forerunner/humanity not being killed off by the Halos. If anything, it's necessary to the narrative.