I understood there to be a difference between peng and peng jing ('the jing'), so am somewhat confused as to the classification of chansi-jin as 'the jing'. Always thought that meant 'reeling energy', which - whilst the hallmark of Chen style - wasn't the hallmark of IS.
There is no such classification. There were other statements of differentiation as well; to support that the classics were mistinterpreted and misunderstood by other prevous masters. Like their comments about double-weighting, it's deliberate - and meant to be controversial.
In perspective-have you ever been in a room with a master level teacher of the JMA, who states that other Master class teachers of a single style got it wrong?