TTX does not pad the final table to a multiple of four bytes. This would cause the Google font checker to reject the font; except it currently has a work-around specifically because of TTX-generated Takao font, which is the default Japanese font on new Ubuntu distributions. In turn, this work-around causes all browsers that use the Google font sanitiser to fail directory-4-byte-002 in the WOFF test suite.
It would be great therefore to
a) fix this in TTX
b) for the Ubuntu folks to remake Takao font with the fixed TTX
c) for Google to remove their workaround
d) for WOFF to meet its Candidate Recommendation exit criteria and become a W3C Recommendation.