Originally, editor Marco Palmieri only intended "relaunch" to apply to the big promotional push that started off the new post-finale DS9 novel series: "relaunch" = new beginning, a single event that would kick off the new ongoing series of DS9 adventures. But as so often happens, the public confused that idea for the overlapping idea of the series itself as a whole, and so people started using "Relaunch" as a designation for any post-finale series, even well after its launch.
Thus, as far as TNG goes, I think the term "Relaunch" is generally only applied to the post-Nemesis
books beginning with Resistance
(or Death in Winter
, depending on how one defines things).