WAV is certainly lossless - it's about as lossless as you can get
In practice and for the scope of this question/topic you are right that wav will almost always presents itself lossless.
But, theoretically it doesn't have to be, since wav is a container format.
Usually it contains pcm (lossless), but it can also contain lossy audio codecs such as gsm and mp3 codecs or even lossy surround channels.
Please consider this a useless addition to this topic, but, facts are facts and knowledge is power ;-)