Yes, true planned obsolescence has happened. But it’s a lot less common than people think, and often prohibited by law.
Even the “slowing down of old iPhones” is an example of that. This was a bug fix for crashing due to current demand that exceeded the battery’s capability.
Most people aren't even aware of planned obsolescence. There's also very little data on how much of this actually happening as no company will admit to this practice. So really no one can make a statement on whether it's common or uncommon without a big data gathering effort.
The statement we can make that is very realistic is that companies are incentivised to do do "planned obsolescence" and because of this "planned obsolescence" has happened, is happening and will continue to happen in the future.
Even the “slowing down of old iPhones” is an example of that. This was a bug fix for crashing due to current demand that exceeded the battery’s capability.