I wish author was a little more constructive here. What phone number pattern would he recommend we use?
Why use any pattern? Let me enter the phone number in a way I got used to it and deal with it.
As suggested in a comment on a rant I wrote a few years ago, one strategy is to 'validate' against something reasonable, but instead of rejecting anything that fails, ask the user to confirm that they really do want something unexpected.
I'm not sure that 'reasonable' would be for an international phone number, but whatever you pick based on the country they choose, let them override your validation.