YMMV. My diet to manage IBS has minimal amounts of fiber. The focus on fiber of the past few decades has been mostly sales driven (i.e. breakfast cereals), the research is quite lacking. As usual in dietetics, no size fits all.
I’ve never heard of a low fiber diet for IBS. In fact the first dietary suggestion on the non-profit IFFGD’s website is to increase fiber intake:
https://aboutibs.org/treatment/ibs-diet/dietary-fiber/
I have heard of people having problems with fiber if they rapidly increase intake or if they don’t drink enough water. I target 1.5 to 2 gallons of water per day.
As you said, everyone is different but you’re just the first one I’ve heard aided by a low fiber diet.
You've never heard of a low fiber diet, I've never heard anybody recommend that amount of water. Again, no size fits all.