GNU tar and PITR

http://developer.postgresql.org/pgdocs/postgres/continuous-archiving.html
says:

"""
Also, some versions of GNU tar consider it an error if a file is changed while
tar is copying it. There does not seem to be any very convenient way to
distinguish this error from other types of errors, other than manual
inspection of tar's messages. GNU tar is therefore not the best tool for
making base backups.
"""

However, GNU tar returns 2 for a real error and 1 for the file changed case.
Isn't that sufficient?

--
Peter Eisentraut
http://developer.postgresql.org/~petere/