Good question. I'd guess that typically people refer to the ascending aorta if it is ascending/root. People get aneurysms in the descending and abdominal aorta too. From what I've read, some people get aneurysms of only the root, some of only the ascending portion, and some get both. For myself, both the root and the ascending portion are enlarged. The root is a couple of millimeters smaller than the ascending portion.

I'd also guess that some people aren't sure because they may only have the information that their doctor gave to them, which may not include which portion is enlarged -- only the largest dimension.

If you go to start reading about it, the root and the ascending portion appear to be very different things. You can get information about either.