RNY-to-sleeve revisions happen, but it's apparently mostly because of severe reactive hypoglycemia and other really weirdly specific complications.
Sleeve-to-RNY is more common in part because the sleeve was eventually conceived as a safer surgery to give people with much higher BMIs, with the intention of converting them to RNY once they lost enough weight that that was a safe option for them. They started doing it as a standalone procedure when many of those patients opted not to come in for the second surgery, being successful with just the sleeve. But sleeve-to-RNY absolutely does happen, still, especially for people who have uncontrolled GERD or who can't lose enough weight with the sleeve alone.
In my pre-op testing they found some small lesions in my esophagus, which might have been esophagitis or might have been a small amount of GERD. I went with the sleeve despite that, because I also have arthritis and might need to take ibuprofen and other NSAIDs again, ever, in my life. (Also, I had been taking large amounts of NSAIDs over a long period of time, and they may have been responsible for some of the damage they found.)
I can't tell you how that turned out for me, since I'm only a week post-op, but I will say my doctor didn't try to sway me toward RNY at all, and given that I also had a hernia repaired, I'm pretty hopeful that it'll all turn out OK.