Even if it wasn't actively downloaded you could theorize that Tuvok's Tricorder (or the ship's computer) would automatically network with the Raven's database.
...However, compare this to TNG "Second Chances" or "Hero Worship", where a specialized, Jerry can -sized device is required for downloading the database of an installation or a ship; needs to be physically plugged in; and takes quite a bit of time to accomplish its task.
The species designation for humans was too high, which was probably laziness or retcon from the low number for Ferengi
The Borg are supposedly "hundreds of millennia" old (TNG "Q Who?"), and/or into assimilation for at least a millennium ("Dragon's Teeth"). Surely they ought to be into six-digit species numbers by now anyway...
Yet note that the Kazon get a number despite not actually being assimilated. Supposedly, the Borg survey various species, evaluating them for assimilation potential; perform regular scouting runs every ten thousand years or so; pick up the pace when the species starts to develop interesting tech; provoke the species into further effort by making piecemeal "attacks"; and finally, after all the potential for learning new skills has been drained of the species, assimilate every last member of the species, thus improving their quality of life as they promise.
Humans could have been surveyed at any point in their prehistory and assigned this species number - quite possibly, the Borg studied Earth long before Stonehenge or Göpekli Tepe was built, and decided to revisit a few thousand years later.
Timo Saloniemi