It actually makes for a fascinating read. Tengen couldn't abide by Nintendo's draconian licensing terms so they essentially stole the information necessary to develop the workaround for NES10, etc. Read more on something like
1up,
overview of Nintendo lawsuits through time,
Wikipedia profile for Tengen, and plenty of other sources.
But that's pretty much what I meant, so far I haven't seen anything that actually _tells me_ arm7 is involved in any sort of copyright protection scheme, and from my general reasoning I suspect it's mere coincidence. The fact that arm7 has become synonymous with copyright protection appears to be rampant speculation.
R4's geographic location could be relevant, I've seen countless stories about commercial and political attempts to fight piracy over there. All the actual efforts I've ever seen though are aimed at bootleggers. Some guy selling bootlegs of Final Fantasy games or The Little Mermaid on DVD isn't the same thing as developing a third party backup/homebrew device, and all the actions from companies like Nintendo seem to suggest they don't perceive them as the same.
Again, I think it comes down to convenient excuses. We see a lot of those around here. And like you said, none of it changes the fact that we still had Guru running around telling people a much different story when DS-X went on market.