Using wrap-file causes the build directory to have the first path from the archive that was extracted. Normally this isn't a problem, but to use gi-docgen with our subproject we need to a --add-include-dir to gi-docgen which means we need to have a known path. These directories with the version number in them would then have to be updated for every gi-docgen call every time we update one of these dependencies.
This is a nightmare, so for the packages we do this for, we will continue using wrap-hg or wrap-git so that can can control the name of the directory for the subproject in the build directory.

Build the docs many times while making sure my $topsrcdir/subprojects directory only had wrap files.