Wiz, that differentiation does not apply to all IP's, and those that make it change tack too.
As things stand, bearing in mind there has been no challenge, so no precedent, all of the PPI is due as an asset of the arrangement. It matters not what loan it relates to or whether it was in the IVA or not.
As this saga has evolved various IP's have used various approaches, sometimes changing their approach mid-stream.
None are contractual or binding, other, arguably, than the "all due to the IVA" approach (until tested).
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014