This is a dialectical difference between Britain and the US.
In England, "Asian" is always used to refer to people we would call "South Asian": Pakistani, Indian, Bangladeshi, etc.
Persons we would call "Asian" in the USA are always called "Oriental" in Britain.
In my America, oriental was commonly used in reference to Chinese, Japonese, Koreans, and Philipinos when I was a kid. Asians is a term I've only hear in the last twenty years.
My take on the British use of Asians is that it's more vague than the common term Pakis. The British press and Politicians are simply using it as a euphemism.