I have a question / opinion for you.
This is the PENALTY : Strike. A 10- foot arc shall be inscribed in front of home plate, from the first to the third base foul line, and any batted ball which does not travel beyond that line will be considered a foul-strike for the purpose of this rule.
So if a batted ball were to settle on the arc. Would this be considered a fair or foul ball. In my opinion it would be a foul due to the definition of the word BEYOND. Meaning PASSED.
WHAT do you think?
This way out of my area of expertise. But I do know a few things that are universal between baseball and softball. The lines that define parts of the field are completely within the area they define. I think a ball that is touching the line, based on the rule you cited, when it stops, would be a foul ball.
This would be consistent with the rest of the rules involving marked parts of the field.