What's wrong with having 2 PNRs if the fare rules don't allow end-to-end?? The only downside I can think of is when the first flight is delayed, then one would miss the "connecting" flight. However, in situation like this, then it would be wise to book extra connecting time.
LAX
I don't think that the comment was intended to suggest that one should or should not use a single PNR. It's simply a question of whether one could use a single PNR. If one can, it's not likely a violation of the COC.
The real issue is not the routing, but the underlying fare restrictions. If the impact is to circumvent minimum stay, it will generally (although one needs to read the COC for the specific carrier) violate. If not, then not. The PNR alone isn't determinative and UA's anti-fraud software is much more sophisticated than in the past.