Nobody is going to deliberately sabotage their LED bulbs because nobody really has a monopoly on them. They probably use cheap components that are only rated for the warranty period, but that isn't "planned obsolescence".
I think it gets worse as time goes on, because manufacturers gain experience with the lifespan of their components and learn exactly where they can cut. If you’re not quite sure how long something will last, you’ll probably err on the side of caution and engineer it to last longer than needed in case you got it wrong.
However, as the article notes, people may not be interested in paying a premium for a product that lasts 10y instead of 5y or 20y instead of 10y, since the tech can change or maybe it’s susceptical to other kinds of degradation.