Earlier quoted context omitted.
I think you're mistaken. They are on Android so it seems odd they wouldn't be. The ability to zoom to arbitrary levels with no pixellation seems to imply it most definitely is vector.
I am using an Android device. And I do clearly see pixelation when I zoom in, before the new tiles load. Here's a screenshot I took after I enabled airplane mode: http://i.imgur.com/wc5Ie.png
I don't see these blurred pixels on my phone, but note that this kind of rendering can also happen with a vector based map: The application has to convert the vector information to a bitmap anyway, for a given zoom level. When zooming in, it is possible that the app shows a zoomed-in version of this bitmap while it is generating a new one in the background.
By the way, it is not necessary to answer every single comment with a link to your screenshot. It is annoying to see the same thing repeated 5 times when reading the thread.