True, but it obviously can't send people beyond the nova, even if at earlier times the Library had disks of the future. But having disks of things yet to come doesn't really sound like a library any more.
On the other hand, if someone from, say, the last year of Sarpeidon sent discs linked to points from its recent past to somewhere in the more distant past … it's not clear to me that would prohibit the traveller in the far past from moving to her future/the disc's past.
This could create the Somewhere In Time
style closed-time-loop paradox about where the library's discs come from, certainly.
That's clever, but maybe those disks wouldn't work, same as the phasers didn't work. Also, could be that preparing certain kinds of tech wouldn't help either. For example, maybe the phasers would stop working as soon as they were prepared.
Since "Atavachron" is a coined Latin-Greek hybrid word that literally means "to regress in time," I assume that's what it does.