You seem to be doubling down on aggressive ignorance of human physiology. You can believe what you like but what you're proposing is simply nonsense in the general case, more akin to alchemy than anything resembling actual science or engineering.
"single finger prick drop of blood at levels that consistently correlate with venous levels" is definitely not one of the fundamental laws of nature. They may not correlate but maybe it's possible to acquire the information about the body through some other channels. It's not like there's a single way of surveying the body, right? A specific test can be impossible but another method can be develop for obtaining the same information.
Blood test nerds can be disappointed, of course. I doubt that the core audience are the blood test aficionado, but you can always make them happy by saying "We are confident that the test can be done through single drop of blood in 2 years".
If a doctor needs the patient's current platelet count for treatment they're not going to be able to get it through a nasal swab or urine test or whatever. This is restrained by fundamental physical laws. If you're still not getting it then all I can suggest is taking a remedial biology course.