After using my Helix for a few days with no ejaculation, my Wife and I had intercourse last night and I had the helix in during. I tried to bear down on the toy as we were in the act, and it felt fantastic. I came soooo hard. But afterward, it felt like there was a bunch of empty space once I took out the aneros. I suppose that is probably normal, considering my prostate was full and swollen, and then empty, but it was strange enough that I felt I should ask.
I think I know what your saying it's like the pressure of an engorged prostate is gone? I've had this as well.
After a good session, and maybe more often if I didn't ejaculate during that session, I also feel an empty space after. If I lay there and focus on the feeling, I can sorta feel like the walls of my rectum / anal canal slightly moving and adjusting, and just lightly tingling and touching each other. It's a nice sensation, and can lead to a-less orgasms. I can have lots of a-less sessions without the empty feeling like that though, this is just a good way to start an a-less session hands free since the stimulation is happening. In general, it's a very subtle feeling.