No it didn't hiccup at all taking the root off. I take roots off like that all the time with tridents, elms and hornbeam. Just cut them off right when the leaves are unrolling in the spring. maybe day three after they pop. I cut off roots like that up to 3/8 inch across with no problems. The tree is pushing so hard right then it doesn't even know you did it. Within about two weeks there will be many roots pushing right below that area. I mention those three plants only because those are trees that thrive well for me where I live, my soil and my fertlizer programs. Your milage will vary.
That tree went on to recieve a ground layer a year later anyway as the roots on inspection the next year was a huge claw. No way it would ever fit into a shohin pots like it was.