You're not alone. Many others feel the same way you do. It's seriously hard-core doggy fantasy land (Meaning MANY women have this as a go to image). But, you have it 100%, it's NOT dog behavior in any way but, in a highly controlled environment, close (some semblance) is possible. I spend a LOT of time explaining that there is no way that her (whatever her I'm talking to) scenario is going to work or happen. We can do certain things to...spice it, but beyond that, it's not a real world scenario for 95% of the folks out there practicing. And, anyone familiar with dogs knows that a dog with this posture *outside* that controlled environment is not the dog you want, particularly, if it's a big dog.
But, I love the scenario myself, so....what can I say?