The support that cssc provides for binary files allows the controlled file to contain any sequence of bytes. That doesn't imply that the controlled file is used for any particular purpose. For example, JPEG files can contain non-ASCII acharacters.
This should be contrasted with support for executable files,
which have a specific Unix file mode bit set (see the manual page for
chmod for more details). Unix executable files may or may not
be binary files. It's common to control shell scripts with
cssc, for example. Shell scripts are normaly executable but not
x flag is set, cssc will generate a g-file whose
execute bits are set. This feature exists for compatibility with SCO
OpenServer's sccs. Do not use this feature if you wish to
interoperate with other implementations of sccs. Setting this
admin -fx generates a warning about this.