Why? Lingering on the battlefield would be the absolute last thing a surviving starship would attempt. Chasing after the Cube would be one possibility, either with the intent of keeping on firing, or with the intent of joining defenses at Earth; realizing that resistance was futile, and heading in the exact opposite direction at maximum warp with survivors onboard, would be a more realistic one.
If the surviving ships took the first option, they probably were no longer surviving when the E-D reached Sol. If they took the second one, they would have refused to answer the hails of the E-D, suspecting a Borg ruse or at the very least fearing a comm trace that would compromise their escape.
Obviously they weren't at Wolf 359 anymore, as there were no intact ships, and obviously they didn't pursue. The best course of action would have been to retreat to somewhere else, but not in a tuck-tail fashion. If they were retreating, it's probable that they would contact any other Starfleet vessels and try to mobilize a fleet to engage them at Earth. Contacting Enterprise, the flagship, would've been a great bet. The Borg didn't care about their communications, and they probably didn't even consider them a threat, so they wouldn't go out of their way to try and stop them. For them to just go and hide would be dumb, and Captain Amasov would've been completely stripped of rank.
It's just not the best explanation. If one really wanted to explain the difference, aside from rounding, there are many other more plausible answers. I found it strange that the Encyclopedia writers would make such an assumption based on such limited info.
In First Contact, Picard does suggest that there have been multiple Borg assaults on the Federation -- he had that speech about how "every time" they pushed forward and Starfleet pushed them back. There may well have been other Borg incidents that we weren't shown in TNG. It's a big galaxy, and not every important thing that happens in it would happen to starships named Enterprise. (Or Defiant or Voyager.)
I don't doubt that there were other encounters by ships other than the Enterprise
after BoBW. But the way the episode plays out is that this is the only contact with the Borg since System J-25 (again, aside from the Lalo). This is evidenced by what Hanson says:
"We expected much more lead time.
Your encounter with the Borg was
over seven thousand light years
away..."
There obviously hadn't been any contact in that period.
About Picard's lines in First Contact, they are this:
"They invade our space and we fall back. They assimilate entire worlds and we fall back. Not again. The line must be drawn here."
Not much can be assumed from this really since it is mostly rhetoric. If "we" means the Federation and not just living species in general, then how does the Federation fall back when worlds unrelated to it are assimilated? I don't see how these lines relate to there being any other major encounters without a wild amount of speculation.