Perhaps it could simply be that the painter was painting in an era where the dynamics of blood circulation were not known - however, i'm pretty sure people in van Dyck's time and even van Dyck himself had seen dead bodies - and all saw that blood didn't flow after death.
Anyway - is this an interesting conundrum or just poetic licence? I only raise the issue because so many 'theories' about the mystery of Rennes-le-Chateau or Rennes-les-Bains arrive back at the idea that the historical Christ is buried in between the environs of these two villages. Lincoln first reported these ideas in his 1982 book 'Holy Blood, Holy Grail' saying that there were persistent legends of Jesus' mummified body being buried in the area.
Also the other obvious point of interest in regards to the painting. The Magdalene has been left out. The painter however made no attempt to re-portray the hand of Christ - as if a dead Jesus could hold up his own arm and hand! So, in respect of the many legends of Mary Magdalene being in the area - perhaps she is the important point to note?
Also she has been removed so that the viewer can see a local landmark of Rennes-les-Bains. Is there anything being intimated here?