There are a couple of issues to address.
Firstly, the PCC does not consider the actual playing conditions, it merely looks at the scores posted and compares them to the expected range and deviation of scores. If there's a big enough difference between the two, a PCC adjustment will be something else than 0. I'm fairly certain the Competition Scratch Score in CONGU worked in a similar fashion. It should kick in in about 5-10% of the days. At my club it has affected 8% of the days on the easier course and around 25% of the days on the tougher course (which doesn't fit the rating system very well).
Secondly, for some odd reason CONGU decided to count the Course Handicap using the formula CH = Handicap Index * Slope Rating/113. As far as I'm aware, every other authority stuck with, or like the USGA, moved to the equation CH = HI * Slope/113 + (Course Rating - Par). Because you don't have the (CR - Par) adjustment in the UK, your Course Handicaps don't really work as a way to compare the difficultness of two different courses and sets of tees.
When they designed the whole Course Rating System, their studies showed that on average players' scores went up by 1.13 strokes for every one-stroke increase in their handicaps. Thus the divisor 113. But because that divisor is used, the Slope Rating needs to go up by 11.3 points for a 10 handicap to receive an extra stroke because of the Slope. A 5 would need the Slope to go up 22.6 points to get an extra stroke but for a 20 only a 5.65-point increase is needed.
For example, a par 72 course with a Course Rating of 70.7 and a Slope of 123 is more difficult to a 10 handicap than a 69.2/138 despite the player getting more strokes on the latter (11 and 12 respectively) in the CONGU WHS. If you included the CR - Par, the same player would get 10 and 9 strokes respectively.