Aside from the fact that this article originally came from a sensationalist tabloid (the Sun), there is only the word of the one person, without even a quote from his girlfriend. The whole thing sounds fishy.
It doesn't sound fishy at all.
Border patrol routinely check through people's documentation to see if their stated reason for visiting is supported. This person claims to be visiting temporarily, but has sent text saying he is moving to be with this woman and never wants to leave her: this is enough for entry to be denied. This is not an uncommon experience.