"Blood thinner" usually refers to something that impairs coagulation or blood clotting. Nicotine does not affect blood clotting as far as I know. Neither do propylene glycol or glycerine. I might be wrong.
I did find data showing that
reduced exposure to cigarettes, by means of using some sort of electric
tobacco cigarette (I'm not sure what that is exactly, a
tobacco vaporizer of sorts) reduces the otherwise abnormally increased red and white blood cell counts in long time smokers. Smokers have increased counts of these cells due to many causes - as an adaptation to carbon monoxide from cigarettes, and due to inflammatory action of stuff in cigarette smoke. This reduction in counts could be referred to as "blood thinning" but it's a "good thing" on one hand, and it's an effect of reducing exposure to cigarettes, not of using that vaporizer in itself. There's no such data about "our"
vaping, but I wouldn't be surprised if the same occurs - after all the avoidance of cigarette smoke is what "thins" the blood in this context and meaning.