No, the I/O shield isn't always in the same place exactly. It depends on the orientation of the mobo. Some mITX have a flat mobo, it lays on its back, so the I/O shield is proportional to that. There's even cases that have down or up pointing ports and even some where the mobo is upside down, so looks like a BTX instead of an ATX case, the window is on the right, the gpu has the fans on top.
But as far as spacing goes, the I/O shield will be exactly lined up with the mobo, no matter how the mobo is situated. This works for whatever mobo the case supports, so if a case supports ATX /mATX/mITX then the I/O shield will mount as appropriate.