What really is the difference? If you know a plastic cog has a 90% chance of breaking after 6 months you're effectively planning on it breaking. You're basically arguing that intent matters more than the effect of creating disposable products.
Real planned obscolescence is making software that requires online authentication and then switching off the auth servers 3 years in so that the customers have to buy a new version. That's a deliberate action.
It can be both. I was in a hardware store looking at painter ladders and noticed many of them had the two sturdy metal ladders kept together by a piece of plastic. Pretty much everyone would think they were extremely durable, while actually the weak link would soon wear to make the entire product useless. Was it incompetence or planned obsolescence? I have no idea, still I wonder why I spotted the problem in 5 seconds straight although I am no engineer.