Based on that FAQ, it appears that they are applying the CWC BPG to all sailings, but they link to the "48 hours from booking" form.
Spot a better price on your booked cruise? Our Best Price Guarantee lets you take advantage of a better price up to 48 hours before your sail date — just give us a call or use our online form. You’ll receive the difference as a non-refundable onboard credit inside final payment or rate adjustment outside final payment.
For more information on the Cruise with Confidence Best Price Guarantee for sailings booked on or before March 31, 2022, that depart on or before September 30, 2022, click here.