I use my iPhone for my wake-up alarm every day ... and have never had a problem with it. I put my iPhone in it’s charging stand, which has speakers attached, and it wakes me up with music every morning.
Of course, half the time I’m already awake when the thing goes off. My internal clock still works very well, indeed. AND, I have a dog who wants to go outside at 6 am on the DOT.
Sounds like you are overly alarmed. :-)