Também encontrei algumas fontes estranhas de 0 byte. Eu encontrei esta explicação:
Back in OS 9 Mac fonts used to store their data in the resource fork. Normally this is used for storing metadata about a file. Someone at Apple decided that putting fonts in there was a good idea. Now in OS X the resource fork has been moved to the extended attribute
com.apple.ResourceFork. Extended attributes are not used in file size calculations by terminal. If you want to see the extended attributes you can usexattr -l file_name. Running that on the font file showed a giant chunk of data in com.apple.ResourceFork that was definitely the font info. Mystery solved.
Fonte: link
Uma maneira de resolver isso é extrair os metadados para um arquivo, assim:
xattr -p com.apple.ResourceFork file_name > file_name.ttf