For awhile while experimenting with a liquid PSMF (kinda like a Lyle McD + Velocity Diet hybrid) that had whole food re-feeds on the weekends (add some Dave Palumbo), I learned that stomachs do seem to shrink.
I remember my first re-feed and eating a half a pizza and about 2 liters of beer.
The next week, I think I had three slices and 2 pints.
Finally, I got down to two slices and a pint... but by the end I was almost forcing those slices to go down.
I attribute this to subsisting on mostly liquid meals for 4 meals a day, only eating about 1700 calories daily (85% protein, 15% fat via fish oil, mct, and flax seeds), then doing everything I could to get in 4k on a re-feed day. By the end, I could not re-feed half of that...
That being said, it did work, it was the fastest 60lbs I ever lost (3 months or so), but I still have nightmares about egg white + ham omelettes with fat-free "cheese", canned chicken, every flavor of protein powder under the sun, and those damn ostra-lean ostrich slim-jim jobbies... not to mention my guts were absolutely WRECKED. Oh, and I gained every pound back, rather quickly once I started lifting and eating like a hoss again (I had decided to lose the weight quickly prior to a shoulder reconstruction surgery).
These days, I seem to go between Paleo IF/CRON and "classic" Paleo 1.0. I've been fairly sated with meals that are only around 400 calories... and I'm finding it hard to get more than 1800 cals a day. Compare that to when I was competing as a strongman and eating 6,000/day. I would say my stomach has shrunk. IF I need calories now I have to make sure everything I eat is as calorically dense as possible.