Is MIAUW the same as a pen test?

The difference between a pen test and the MIAUW methodology.

No. A pen test is a form of security research. MIAUW is a methodology to better structure, record and make such research more controllable.

A pen test can therefore be carried out according to MIAUW, but MIAUW is broader than just carrying out technical tests.

Also read What is a pen test? and MIAUW.