The article is written by a former caseworker and gives an insight into how PAP letters are evaluated.
The article does emphasise to keep the PAP letter nice (not accusing anybody, including other caseworkers of not having done their job, for example) and keeping it simple and short. The caseworker is a non-lawyer who has a lot of letters to go through and as quoted above, it is faster to reject the PAP than to approve it. So, write it in such a way that s/he will want to concede the PAP.Caseworkers are (usually) university-educated with targets, aspirations, pressures, and limits on their time. They are hired with a particular purpose in mind: spot the duff and get rid of it quickly.
In most circumstances, it is easier for a caseworker to defend than to concede. They have only the authority to refuse; to concede that the Home Office was wrong and send the decision off for reconsideration by the relevant team, they need approval from a supervisor.