The size I ordered was the medium with the regular seam length. They have not changed their fabric, and apparently do not have any suggestions for why several people have had pants that weigh very differently.
I am also happy with the pants, given alternatives. Although, I probably would have just gone with a baselayer + wind pants combo had I known they would weigh this much (because I mostly wear shorts, but like wearing pants on occasion).
I've heard of least one other person who received Bone Flats pants that were quite above the listed weight. It must be a quality control issue to be varying by up to 40%.
Edit: I've been told the variation might be from seam allowances from the seamstresses. Fair enough, but seems like a lot of weight for that. Maybe they will now mention such a weight variation on their website.