Could I refer the honourable gentlemen to my and grgkecer's posts Nos 1785 and 1786 re. AKI sources.
Could I also suggest that whether or not the BBC does it properly, source validation doesn't really come into it when AKI is just carrying the content of press conferences or briefings, which is what most of the fuss is about.
So as we decided last time - don't believe literally what AKI tells you, but do regard it as a useful barometer.