The statement in "4.2 File and directory structure":

Publication resources MUST NOT be located outside the publication root or its descendant directories.

is duplicated in "4.4 URLs in the file set"

eBraille file set MUST NOT reference publication resources outside the publication root.

Also, I suggest replacing "as defined" by "as described" in the following 4.4 sentence:

Remote resources [epub3] are not supported, as defined in 3.5 Resource location.

since the normative statement is in "4.2 File and directory structure" and not "3.5 Resource location".

Note that these specific editorial suggestions may become moot depending on the course of action taken for #316.