Wrong.
If you're in front this fails.
Of course if you are turning right you are going to make to make the person behind you brake(/slow).
It's the highway Code as I remember it so it's right, of course it's something to aspire to, but early road position and signal after checking that another road user isn't going to have to do something sudden as a result of moving in front of them is common sense you'd think
I was drawing attention, as BM did, that the look precedes the signal, a signal does not give someone immediate priority to do as they please, as much as many road users clearly seem to think