Actually a probe is a standard military tactic to determine the strength of an opposing force. The probe's intention is to determine reaction time, technological ability, weapons type, discipline, detection, etc.
It's also something that insects do. The 'hive' might send in a single Ant to probe around in a kitchen, and then a while later all his buddies start to come along too. And as we know, the Borg's behaviour was (originally) based on the behaviour of insects, specifically those hive mind species like Ants or Bees.
We also don't know when the Borg destroyed the El-Aurians' homeworld. Guinan said in "Q Who" that the event had scattered her people, and I assumed her visit to Earth ("Time's Arrow") may have been due to that scattering.
The refugees in "Generations" may not have suffered their trauma recently, it could be a long-negotiated removal. Or the first place they went to was unsuitable and Starfleet was helping out with another new location.
I would think the destruction of the El-Aurian homeworld and the events of Generations likely happened in fairly close proximity to one another...
Star Trek: Generations said:CRUSHER: He's an El-Aurian, ...over three hundred years old. He lost his entire family when the Borg destroyed his world. Soran escaped with a handful of other refugees aboard a ship called the Lakul. That ship was later destroyed by some kind of energy ribbon, but Soran and forty-six others were rescued by the Enterprise-B.
Agreed, BillJ. There's very little ambiguity there, the Lakul was apparently escaping from the Borg cataclysm. It's sort of a continuity error, but it was probably an intentional one, for dramatic purposes.