This is possibly configurable, I don't know and didn't care. In GNOME, this is configurable behaviour. I liked this default and kept me on Unity because of that.

This comes down to personal workflows. I got very frustrated dealing with the alt-tab behaviour of only showing windows when my focus is what application I need to use when I do the alt-tab. This is also the one holdover from using OS X daily, the one feature I felt was right (really, for me and probably a lot of people.)