The law has read that way for years, and the tax should not be on the GFE in WA, because the statute specifically makes it an obligation of the seller.
Here are the changes to the statute made this year (which don't have anything to do with this issue):
RCW 82.45.080 and 1980 c 154 s 3 are each amended to
read as follows:
(1) The tax levied under this chapter ((shall be)) is the obligation of the seller and the department ((of revenue)) may, at the department's option, enforce the obligation through an action of debt against the seller or the department may proceed in the manner prescribed for the foreclosure of mortgages ((and resort to)). The department's use of one course of enforcement ((shall)) is not ((be)) an election not to pursue the other.
(2) For purposes of this section and notwithstanding any other provisions of law, the seller is the parent corporation of a wholly owned subsidiary, when such subsidiary is the transferor to a third-party transferee and the subsidiary is dissolved before paying the tax imposed under this chapter.
Nobody's perfect, not even a perfect stranger.