Masteron doesnt act as an Aromatase inhibitor (AI) nor does it lower e2. It changes the androgen/estrogen ratio which can help in gyno prevention. It should in no way impact your Aromatase inhibitor (AI) dosage nor should it be used in place of or as an Aromatase inhibitor (AI) in my opinion.
Some people CAN get away without using an AI, whilst using mast. However, I wouldn't recommend it as you may find yourself in trouble doing so. Well worth it to continue using an AI in my mind