Hmmm... not too sure what you are looking at, but as long as you are fully vaccinated and boosted in the U.S. (and if you are going in the UK, you need to be boosted), you have 3 days in the U.S. also:
https://www.princess.com/plan/cruise-with-confidence/cruise-health/frequently-asked-questions/us-cruises/?accordion=covid-test-prior-to-boarding
COVID-19 Testing Requirements
UPDATED: Will I need to have a pre-travel viral COVID-19 test performed prior to boarding the ship?
Yes, in accordance with CDC directives, ALL guests ages two and above will be required to produce a negative viral COVID-19 test result (PCR or antigen) taken before embarkation. Testing requirements for voyages departing from the U.S. are as follows:
Vaccination Status
CDC Definition
Pre-Travel Test-Type
When to Take Test Before Boarding
Fully Vaccinated
Received primary series of COVID-19 vaccines with final dose at least 14 days before embarkation
Antigen
Within 2 days
PCR
Within 3 days
Up to Date
Received all recommended COVID-19 vaccines, including any booster dose(s) when eligible at least 7 days before embarkation
Antigen
Within 3 days
PCR
Within 3 days
Not Vaccinated
Not fully vaccinated
PCR
Within 3 days