Сценарий init не работает от PWD

Введите man bash и прочтите документацию.

Что вы найдете там:

   if list; then list; [ elif list; then list; ] ... [ else list; ] fi
          The  if  list  is  executed.  If its exit status is zero, the
          then list is executed.  Otherwise, each elif list is executed
          in  turn,  and  if its exit status is zero, the corresponding
          then list is executed and the command completes.   Otherwise,
          the  else  list  is executed, if present.  The exit status is
          the exit status of the last command executed, or zero  if  no
          condition tested true.

Это означает, что после , если может быть любая команда, и bash заботится только о возвращаемом значении этой команды. Выше вы использовали две разные команды: [ и [[.

   test expr
   [ expr ]
          Return a status of 0 (true) or 1  (false)  depending  on  the
          evaluation of the conditional expression expr.  Each operator
          and operand must be a  separate  argument.   Expressions  are
          composed  of  the primaries described above under CONDITIONAL
          EXPRESSIONS.  test does not accept any options, nor  does  it
          accept  and ignore an argument of -- as signifying the end of
          options. [...]

Это классический тест, доступный во многих оболочках.

   [[ expression ]]
          Return  a status of 0 or 1 depending on the evaluation of the
          conditional expression expression.  Expressions are  composed
          of  the  primaries  described below under CONDITIONAL EXPRES‐
          SIONS.  Word splitting and pathname expansion  are  not  per‐
          formed  on  the words between the [[ and ]]; tilde expansion,
          parameter and variable expansion, arithmetic expansion,  com‐
          mand  substitution,  process  substitution, and quote removal
          are performed.  Conditional operators  such  as  -f  must  be
          unquoted to be recognized as primaries.

          When  used  with [[, the < and > operators sort lexicographi‐
          cally using the current locale.

          When the == and != operators are  used,  the  string  to  the
          right  of  the  operator  is considered a pattern and matched
          according to the rules described below under  Pattern  Match‐
          ing,  as  if  the  extglob  shell option were enabled.  The =
          operator is equivalent to ==.  If the  shell  option  nocase‐
          match  is  enabled,  the match is performed without regard to
          the case of alphabetic characters.  The return value is 0  if
          the  string  matches (==) or does not match (!=) the pattern,
          and 1 otherwise.  Any part of the pattern may  be  quoted  to
          force the quoted portion to be matched as a string.

Это расширение в bash с немного другим значением. В частности, == определяется по-другому. Первый выполняет буквальное сравнение, а второй - сопоставление с подстановочными знаками.