Ann: Pioneer and Senior Financiers to extend Standstill Agreement, page-19

I don't think your description of PNC is accurate regarding always buying new debt vs collecting old nor the lack of hanging back on purchases when prices don't suit.
This is exactly what PNC does, you'd know that if you read the shareholders presentations over the years.

All companies 'hide profits' during good times to smooth out blips, it's just some are better at doing it subtly. PNC quite clearly didn't show a good performance early in FY19 if you read their interims.

PNC does not sell future cash flows.

CCP share price is trading around a 10 year high.
CLH is trading at 50% of 10 year high
.I think a lot of what you have posted is more closely related to CLH than PNC.

The 'unique business model' I believe was referring specifically to their ethical approach to dealing with their customers, nothing else. This was one aspect of PNC that attracted me to investing, I don't believe it is mutually exclusive to running a highly profitable & successful business in this industry.