I think term 'split up' might be misleading. The LW aircraft were apparently forced to fly evasive tactics, unlike the rigid formations of the USAAF later on. But the raids as a whole continued to their target, they didn't scatter before doing so.
That said, official reports record that on a number of occasions, raids missed their targets completely, and minor raids were driven off and jettisoned their bombloads. However I can't any reports of a major raid being wholly split up.
The official air ministry account from 1941 wildly exaggerated the numbers shot down - they must have had access to local reports of any crashing aircraft, so was this just a bit of propaganda ? If so it was pretty pointless, coming so long after the event.