When invoked that way it still supports more than /bin/dash on my system:

  % ln -s /bin/bash sh
  % ./sh
  sh-3.2$ echo {1..10}
  1 2 3 4 5 6 7 8 9 10
  sh-3.2$ exit
  % dash
  $ echo {1..10}
  {1..10}

where dash is supposed to be POSIX compliant.