Isn't it normal in Europe to consider a person "Irish" or "Dutch" or "German" even if their family has been in England for generations? and wouldn't black Jamaicans be considered Africans?
We all know that truth and common sense do not apply to Leftist. And Britain along with most of Europe is Left leaning. Therefore, they will jump through hoops to deny or obfuscate reality, as is normal for the Left.
They say 'Asian' or 'youths' because they want to hide and downplay the obvious danger posed by Islam. They cannot bring themselves to face Islam for what it is and what Islam does. They prefer to deny it and to pretend that it is not happening.
This case is a double hit for the Left, because not only is he Muslim but he is also Black. This gives them two facts that they have to play down and try to cover up. I know that there are Liberals all over the world who are angry about this. But Liberals are not angry about the death and injuries of this horrible act. The Liberals are only angry that it was not done by a White Christian. Because a White person doing something like this would validate their fictitious, fantasy-land, worldview, and would give them ammunition to defend daily Muslim atrocities for the next fifty years.