The gaps will move a bit, yes, because the spacing will change a bit. As you know, Dorico adjusts the horizontal position of lyrics as much as it can to prevent the rhythmic space from becoming distorted by the text, but as soon as you apply any kind of horizontal offset to a lyric, even a zero offset that doesn’t move it, all of that wiggling is disabled, and the lyric will often cause the spacing to be widened locally in order to meet the minimum requested space either side of the lyric as specified in Engraving Options.