Quite so. In "BoBW", Shelby and Data establish that the scooping up of the Jouret colony was done by the same folks who scooped up the J-25 civilization, but they don't claim that the forensic evidence would also connect the Neutral Zone outposts to the same perps. In fact, later episodes don't mention the RNZ incidents at all.
It should be noted, though, that what was destroyed at the RNZ was a series of "outposts" and "starbases", not colonies. Also, throughout the first season of TNG, something was amiss at the Neutral Zone - references to it were made in "Heart of Glory" and "Angel One" - so Starfleet would probably have been devoting resources to these bases. If top-notch Starfleet military technology was what makes the Borg hot and bothered, then, they would have gotten a taste of it from those installations already. In that case, the "Q Who?" encounter would not have been an important milestone.
Of course, we may be completely mistaken in the assumption that something triggered the Borg interest. For all we know, the Borg had already written down an assimilation schedule three thousand years ago: "1000 years from now, go see if use of iron is widespread. 2000 years on, check on progress in global transportation and spreading of agriculture to hostile climes. 2500 years from this point, see if there's any industry or EM activity. Depending on results, increase the frequency of visits. Assimilate when warp tech surpasses Specification 8882B or the Exotic New Tech Index reaches 12.5. " The RNZ scoops and the "BoBW" invasion may have been scheduled events.
Timo Saloniemi