Eu não acho que você esteja perdendo nada, a questão óbvia é que nenhum dos campos de dados não citados deve ter qualquer possibilidade de conter o caractere separador. Se algum dos campos de dados citados puder conter seu caractere separador, será necessário usar um método menos eficiente para separar os campos posteriormente.
Tab deve ser relativamente seguro
Note that in httpd 2.0 versions prior to 2.0.46, no escaping was performed on the strings from %...r, %...i and %...o. This was mainly to comply with the requirements of the Common Log Format. This implied that clients could insert control characters into the log, so you had to be quite careful when dealing with raw log files.
For security reasons, starting with 2.0.46, non-printable and other special characters are escaped mostly by using \xhh sequences, where hh stands for the hexadecimal representation of the raw byte. Exceptions from this rule are " and \ which are escaped by prepending a backslash, and all whitespace characters which are written in their C-style notation (\n, \t etc).