Yes - you need to begin and end in the same point but your itinerary can consist of a combo of one-way / round-trip tickets. From the Trip Cancellation and Interruption Insurance Terms for the Platinum Card... (some of my emphasis added)

"To get coverage: You must charge the full amount of a Covered Trip to your Eligible Card or in combination with your Eligible Card and accumulated points on your Eligible Card or redeemable certificates, vouchers, coupons, or discounts awarded from a frequent flyer program or similar program.

Covered Trip means a period of round-trip travel to one or more destinations other than an Eligible Traveler’s city of residence at the time of departure where: (1) The Eligible Traveler departs by Common Carrier to begin the period of round-trip travel; (2) the period of round-trip travel ends when the Eligible Traveler returns by Common Carrier to the city of departure; (3) the period of round-trip travel does not exceed three hundred sixty-five (365) days away from the Eligible Traveler’s city of residence at the time of departure; and (4) the Eligible Traveler charges the full amount of the cost of transportation by Common Carrier(s) to your Eligible Card. The period of round-trip travel may consist of roundtrip, one-way, or combinations of roundtrip and one-way tickets with Common Carrier(s)."