I was visiting a young lady of my acquaintance who's oral skills are among the best. She's able to take me right down to the base and says she loves giving pleasure this way. We took a  short break to drink some more wine and as we were returning to bed she did something I've only seen in porn videos but never experienced before.  She got on her back with her head hanging off the edge of the bed and beckoned me to her.  She took my cock in her mouth and encouraged me to fuck her face.  I was concerned I might choke or hurt her so I took it easy, but she was having none of that!  She grabbed my hips and pulled me toward her until I was balls deep fucking her mouth and throat.  Wow!  So I went for it, really fucking her deeply until my legs began to quiver and I couldn't take any more.  I asked her how she learned to do this and she said it just came naturally to her.   No gag reflex whatsoever. She was delighted that she could do something that was new to me. I've been hobbying actively for 14 years and this is the first time I've encountered this amazing skill.  Is it as rare as I think or have others experienced it also?

I had my one and only experience with that last October with Marianna The Muse.

he's the only one I've encountered that offers that regularly.  I was mesmerized by her spinner body stretched out in front of me, took a lot of control to follow her instruction to slide it in really slowly.

... but I've experienced it a few times.  The first time it was with my ATF.  She was the one who suggested it and even fetched a wedge-shaped cushion to optimize the angle. Like you I was concerned about this position being comfortable for her, and she told me she's learned through practice that it's great for her and is the perfect angle to allow her to deep throat.

I've had several providers do this including my current ATF. But I've also had a couple of GF's do it too, both of which really loved giving BJ's.  
BTW it was always the young lady, regardless of profession that suggested this position...

I wrote about it in my blog a few years ago
I think most guys would love to give it a try

positions you can use to accomplish the same result. Nothing like pumping away at a warm inviting mouth.

Hanging her head off the bead and being throat fucked is her signature move

I even love it when I AM gagging and choking.  It's a turn on for me.

I agree it's not that rare. I've had that with many different women.  When they let me cum in the back of their throat is the best feeling ever. I would do a return visit just for that.

Freya Fantasia did exactly the same thing.......

been there, done that, bought the soundtrack.