Who can say what they will ask at POE? There are no set scripts that they follow. The CBP officers have every right to question an individual as to their circumstances. An approved visa allows one to present her/himself at the border. It is still no guarantee of admission. And if the CBP officer feels that the visa has been obtained fraudulently or that the holder is any way ineligible for admission in that particular category, he can deny admission. Look through here at how many people with valid tourist visas have been denied entry or removed because it was believed by the CBP officer that they were not coming here purely for tourism.
I do know of a case on VJ where a K-1 visa holder was removed at the border. During the POE process the CBP officer asked something about working plans,, career, etc. Possibly due to a misunderstanding by the K-1 holder who did not speak English well, she told the CBP officer that she was planning to work here. She probably meant “in the future when I have my EAD” but it was taken at face value and completely literally and she was sent back to her home country.
Off-VJ I am aware of a K-1 case who was asked at the border “are you aware you must marry within 90 days?” (Which is “standard” questioning) to which he replied “well we haven’t decided if we will get married or not. We will use the 90 days to find out”. It was determined that this constituted a lie on his “statement of intent to marry” that he presented to USCIS and the embassy and he was sent back also.