I would like to see the next run have an even length in the front and back. I wear polos often for work, and when I get done for the day, I just like to untuck. The problem is that shirts like this are meant to be tucked and therefore the difference in tail length. The even all around Polos can be tucked or untucked and look completely fine but anyone who truly knows polos, knows this shirt is to be remained tucked, and that sucks.
I know this isn't law, but this is a general rule of thumb like leaving the last button undone on a suit jacket. If you want to, you can fasten it, but everyone who knows how to wear a suit will either correct you or look in disappointment in your direction. When I untuck a shirt with a tail, I know what I'm doing is wrong and looks silly and I try to avoid as often as possible and have stopped buying Polo's with tails as a result.
"Shirts that are made with a flat bottom hem are meant to be worn untucked. But if the shirt has visible “tails” — that is to say, the hem varies in length, rather than being even all the way around — it should always be tucked in."