Turned out that, after the show-off in the pilot episode, that capability was used only in a few episodes and, I dare to say, never in a decisive manner.
Never? Au contraire.
In The Best of Both Worlds, Part II
, saucer separation was one of the tactics employed to distract the Borg, in Riker's battle to rescue Picard, which was a win
It really just struck me as a fanwank, we're doing this because it's cool novelty, than a plot necessity in BoBW2. Just like that anti-matter spread thing, which wasn't ever seen or heard from before or after.