I'm in the minority here but then again I'm used to it. I think it's a horrible thing to do. It's one thing to not look like a POC but when you don't feel like one then you have no business checking that box. What you are saying is that you have white skin privilege, and you have similar if not exact social privilege but that's not good enough so you want more.
Schools have a URM boost because URM's face different challenges than white students. My two best friends are Navajo and Mexican respectively. Even though we face different cultural barriers or assumptions we all deal with the double consciousness that goes along with being the ''other''. We used to call people who did what you did "box checkers". They are the people who become of color during admission and the poof they are gone.
The experiences of my Navajo friend speaks to how this can be very detrimental. My UG had a multicultural life center that we both worked at. Every year we would get a list of all the newly accepted POC's and every year ther would be at least five Native students on the list. She would get excited. They would turn out to be box checkers and she would spend the year lonely. She had no one, no one who had been to a pow wow, ate fried bread, been to an NAC, lived or stayed on a reservation, understood native culture, or could even get an inside joke. No one would fight with her on Native issues except people like me who at best will always just be allies.