Ambiguous in that I’m looking for “go here, do that”! Some of these requirements/codes get to be a LOT of little things to know. Not being someone that installs handrails or guards, this is new information to me. I can see a triangle formed by either the back riser and the tread, or the front riser and the tread. Then there’s idea that 6" seems awfully small - or puts the guard close to the tread - not actually looking at a stair/guard installation. There may be more clearance than my mind is envisioning.
Also, you can’t rule out the “Tom’s a hardhead” angle!
But, looking at it in the lens of safety, and a 6" ball shouldn’t pass thru any part of any riser/tread/guard triangle puts it to bed.