My own feeling is that I've read a number of stories of experienced instructors discovering unrecoverable spin modes in aircraft like the Cessnas.
I'm curious about how these stories would have been written, or recorded. Texted from the instructors' mobiles in the last few seconds of their lives? There's the true story of the Top Gun filming, where someone (forget the name) did radio "I'm really having trouble" before pancaking a Pitts (not Cessna) from a flat spin. Are there really other stories like that?
The big danger with spins is that they go flat. Keeping the CG well forward will ensure that doesn't happen. Recovering from an intentional flat spin is enjoyable but it is kind of spooky seeing the ASI pegged at zero. As long as a spin doesn't flatten, and the aircraft has met the certification requirements, it had better recover.
But there is a huge difference between a one-turn spin (which is really still incipient) and a fully developed beyond-three turn spin. And there are planes (like the Extra - not that I've flown one) that need specific, careful handling to recover.