Well, immigration intent has to do with all visitor or tourist visas into the US. But I still wouldn't say at the K1 interview: "Immigration is the whole point of the K-1...she's traveling to marry and then stay permanently!"
In reality of course a woman will stay there but that wouldn't and shouldn't be her primary reason, or it is better to make a stress on 'marrying her fiance' and following him wherever he lives, and it happens to be the US.
I personally don't look at this as 'immigration'. People who immigrate come mostly to work here or after their relatives. But I personally didn't immigrate here, I came to be with my fiance/husband, to make him happy. USCIS calls it K1 non-immigrant visa.