When you hit Select media button, the dialog appears, informing you about the file max weight and accepted extensions - according to field's settings. However, when the form has been submitted, it expands and shows "Replace file" widget - there the info seems to be ignored.

Comments

I believe that this functionality of the Media module is not intended to limit the size of the image that a user is permitted to upload. But rather, it's intended to limit the size of the image file that's actually stored by the module after upload -- i.e., in particular, the image is resized to match the maximum dimensions. As a result, when you upload an image that's larger than the parameters set in the field, the module will simply resize the image to fit within the maximum dimensions allowed in the settings for the field.