Vax spike proteins are artificial, and they have to make the body create a ton more than you would get from the virus in order to try and simulate the immune response to the actual virus spike protein.
Artificial Proteins Never Seen in the Natural World Are Becoming New COVID Vaccines and Medicines
The first-generation COVID vaccines, including the mRNA vaccines that have been such lifesavers, work by introducing the virus’s spike into the body, without a functional coronavirus attached, so the immune system can learn to recognize the RBD and rally its troops. But the RBD is periodically hidden by other parts of the spike protein, shielding the domain from antibodies looking to bind to it. This blunts the immune response. In addition, a free-floating spike protein does not resemble a natural virus and does not always trigger a strong reaction unless a large dose of vaccine is used. That big dose increases costs and can cause strong side effects.
That said, if you have had Covid and recovered, the spike proteins will be cleared out after some period of time. If you've been vaxxed, they are unsure of how long the body continues to make them, and there are a lot more, but at some point the blood probably clears. If there is a test for the spike proteins, I'd be fine with blood from a vaxxed person who has already absorbed all the spike proteins into their vital organs as long as the blood has cleared.