I will always be a Wyomingite at heart. Currently I'm a Minnesotan by wife. I will always refer to my deer as a 2x2 or a 5x5 or whatever it may be. Here's the best I can figure it.

First, how many deer have you seen that have a different number of points on each side? It's much more descriptive to tell how many points are on each side. Just saying it's a 10 point could imply that there's one weird antler growing straight out of the middle of its head and it has 10 stickers growing out of it.

The other reason, and I suspect this is probably more likely, is it makes the deer bigger.
Example: If you measure a room, you give the dimensions of each side, such as 5'x5'. But technically the room is 25'. Using the same very obvious math, Chets deer is 5 points x 5 points. So Chet, you can refer to your deer as a 5x5 because your humble, but in all honesty that would be a 25 point.