Checkboard:
So, with a 90º intercept onto the arc, you would start the turn at 220 odd knots at about 1.3 miles or so - and may commence descent (as you are within 2 miles).
Given that is the case, it is nonetheless poorly thought out and poorly worded. It should state "...within 2 miles of the arc..." not "+/- 2 miles."
And, two miles from the arc centerline is too far out to begin descent in any case. Descent should commence at the bisector of the turn onto the arc, just as in RNAV.