You are quoting an older draft. The rules applied to 'master'
is actually a bit more lenient:
- Unless otherwise specified, indent with SP that could be
replaced with HT are not "bad". But SP before HT in the
indent is "bad", and trailing whitespaces are "bad".
- For C source files, initial indent by SP that can be replaced
with HT is also "bad".
- Test scripts in t/ and test vectors in its subdirectories can
contain anything, so we make it unrestricted for now.
So your particular "indent without HT" is generally accepted,
and considered a violation only in C sources.
I see what you mean by "excempt from all rules" and it is
certainly a valid approach, but I at the same time think minimal
whitespace policy should be there, and flagging trailing spaces
and SP before HT is a good idea.