I don’t think it’s misleading, it’s likely to be maths. As the front triangle leans back to get slacker, the (horizontal) reach shortens. Meanwhile the slackening of the head angle means the front wheel gets placed further out, and so it’s probably this that means the wheelbase doesn’t change much.
As with most things in our balance sport of Bike, my experience is that the sweet spot is usually in a narrow range. Went from 160 to 170 fork once on a full suss and the 160 was amazing, 170 awful. I’ve a hard tail that’s ‘meh’ at 140 and ‘yeah’ at 160. It’s well worth experimenting and a great editorial :)