Yes you are missing something, UV won't damage the phone, you are being bombarded by UV all the time.
Not putting a filter on it is a very bad idea, but you don't have to take my word for it if you don't want to.
Go ahead and don't use a filter on your phone or camera, just don't come back in here after you've burned a hole in the CMOS sensor and complain about it. I can't for the life of me understand how you think this is a good idea.
"iPhones don’t come with a warning saying don’t film the sun."
Yup, they also don't tell you not to take a blowtorch to it or microwave it, or put it the garbage disposal either.
At some point they assume you have some common sense and don't need to be spoon fed every single warning that could possibly happen.