The UK is relatively unique in that its visa process is an affirmative approval for entry unless fraud is later discovered. The US and most other countries still deny properly-documented travelers.

I certainly don't regard the Daily Mail as an authoritative source and I don't expect either US or UK authorities to comment. But, the bottom line is that had the father not been picked off at the boarding gate, he would likely have been denied entry on arrival at LAS.

These things may appear to be random and casual, but they are far from it. Doesn't mean that this guy is a bad guy. Maybe he is a name match and the same age of a bad guy. So, maybe DHS was wrong. But, still not likely a random selection.