What I have been able to establish is that there was blood on Becky's onesie.
We know that Becky's onesie was removed by NM or SH before she was dismembered, so it is unlikely that the blood got there during the dismembering, unless it was just spatter.
It was reported that there was blood on the straps of her onesie. I thought this strange, to hear the onesie had straps, and that it was short legged, so I tried to find an image of a George (Asda) leopard print onesie to fit this description. I found something that I wouldn't describe as a onesie, but more of an all in one type of nightwear, or lingerie, like a teddy.
I think what they were suggesting is that the neck wounds (screwdriver) bled more than the abdominal knife wounds, but that they couldn't say with certainty when she bled. One possible explanation for this could be that the stabbing in the neck occurred around the time of death, when there was no or little blood circulation. I don't think they were willing to speculate or draw a definite conclusion either way.
BIB If that's true, then either the wounds happened at CH or she died at a later time. I did wonder when NM's defence said this, if he was going to suggest that it wasn't actually NM who killed Becky but that doesn't seem to be what he meant.