It works just fine because in the majority of Final Fantasy titles, EVERY monster has been either player size or much larger. Excluding tonberries, which will most likely be the same size as dodos or marmots here. Also it lets you appreciate the details in all monsters.

There are small adjustments to size to make stronger monsters larger as well. Just look at the next final behest monsters you face. Decently bigger than a normal version of the same enemy. NMs even more so.