Ok, I fear you're being deliberately obtuse, but here goes.
"Reason for interaction" is not a feature. If you think that constitutes a feature, then you're basically arguing that the DDA encompasses any change anyone could possibly imagine, provided it leads to player interaction. For example: magical space rabbits which ensnare players and force them to fight to the death in wormholes. Thus, magical space rabbits are in the DDA. You're basically arguing that the DDA is useless as a manifesto, because you can find a justification for anything in it, because: vague wording. This, to me, is intellectually dishonest. The question you should be asking yourself is: did people in the DDF imagine PP when they talked about player interaction. Given their predominant reaction, I'd guess not. So, you're arguing the equivalent of a legal technicality, which is pointless, because the frustration comes from the feeling that the spirit of the DDA is not pre-eminent in development. This is not a box-ticking exercise. No one is going to say "oh yes, you've managed to shoehorn PP into an extremely vague idea of player interaction, suddenly i feel renewed confidence that the DDA is at the centre of FD's development plan".