Maybe I'm missing something, but I think this makes sense.
You selected the UK, but are entering a number with US dailing code. So it's an invalid number in the UK, but it's a possible phone number since you could select the US instead?
Also usually when you select the country separately, wouldn't you omit the country specific dailing code?
Yeah, I’m in the uk and it was the default cc. I entered a us fictitious number, which gave that error. No variations of uk numbers, with or without the international prefix would work either. This was just the funniest of the validation errors.
And if it can validate international numbers, why ask for the country code separately?
The US number is not valid due to the following rules: “Using 0 or 1 as the first digit of an area code or central office code is invalid, as is a 9 as the middle digit of an area code; these are trunk prefixes or reserved for North American Numbering Plan expansion.“ *
I’m sure you tried other numbers, but the number in the image fails due to that specific reason.