The problem turned out to be me being stupid, and quick to jump the gun on other problems. I dove too far down the rabbit hole, and lost sight of what was happening. I did not include the otf
filetype in the regex, and it wasn't being included.
Facepalm
EDIT:
To clarify: all I had to do was change
if path =~ /\.(eot|svg|ttf|woff)\z/
to
if path =~ /\.(eot|svg|ttf|woff|otf)\z/