They need to be explicitly clear exactly what they mean even if it takes them a couple paragraphs to explain it.
I have both US and Canadian citizenship. I live in Canada. I was vaccinated first dose with AstraZeneca and second dose with Pfizer, in accordance with Government of Canada guidelines.
My sister, who I live and travel with, only has Canadian citizenship. She received two Pfizer doses.
My sister meets the current CDC definition of fully vaccinated, while I may not. But if
DCL goes with "US citizen" instead of a residency rule, when she would need testing while I might not (depending if DCL would allow mixed dosing). Even though we live and travel together. Which makes no sense.
Plus what about all the non-citizens who live in the US ? Permanent Residents (i.e. "green card" holders), people on work or student visas, etc etc ? If the rule is for "US citizens" would that mean they have to be tested even though they live in the US ? Really DCL ??
So they really do need to clarify their expectations/intentions. Explicitly and clearly, so there are no gaps and confusion.
SW