SUSA rule 1.5. The batter's box is the 3' X 7' area to which the batter is restricted. The lines are considered as being within the batter's box. At least some portion of both feet of the batter must be on the line or within the batter's box.
Questions: What is the official ruling if a batter's foot or feet are outside of the batter's box? Is he/she out? Assuming the umpire provides the batter a warning and he/she still is outside of the batter's box when the pitch is delivered what should the umpire do?
Read 7.5 C it might help. Maybe not I don not know.
Please see Official Rulebook §7.3 A. for the very clear and easily understood RULE in this fact pattern. You quoted §1.5, which is a DEFINITION and not a rule. The batter is OUT if (s)he makes bat contact with the ball, regardless of the ball ending up fair or foul.