I don't know why that's completely different - that's the behaviour I was describing.

“if that person doesnt know your number“

I’m saying that if two people have each other in their contacts lists and are on friendly terms, it’s not rude to call them if you need to talk to them.

Maybe I misunderstood, though. Sounds like you were talking about cold calling someone you don’t know. I agree that’s rude if the person is not expecting random inbound calls or isn’t in a professional context were there’s an expectation of receiving a call, and has been for generations.

Yeah, it's subtle. There are friends I can call out of the blue no problem, and others that I definitely need to text first. Generally determined by how well I know them, or in what context I met them. If it's someone I haven't called before, I'd consider it rude to just call them without texting first.

And, obviously, in a work/professional/commercial setting it's always OK to call if they've given you their number. It feels weird, but it's OK.