I'm sitting between my hplc and gcms, if you think pH and acidity (both carefully controlled for by the body) have nothing to do with absorption you might have very little experience with lab sciences.

It's about much more than viscosity, it's about evaporation rate, chemical balance, and yes some absorbency. I would say just using generic human blood isn't enough, the chemistry within the vagina is self regulated like no other part of the human body, it's kinda the key organ to life's continuance.