They are, but it's nuanced. If you have one app with a single window, it will always be selectable via Cmd+Tab, even if it's full-screened. If you have an app with multiple windows, one of which is full-screened, and you select a non-full-screened window from that same app, you won't be able to return to the full-screened window using Cmd+Tab. Which kinda makes sense, since Cmd+Tab cycles apps, not windows.

I am going to put in a plug for “Which” a command tab replacement that lets you, among other things, cycle between windows like alt-tab.