For certain values of “obvious”. This first graph in this paper shows the annual incidence of vCJD, the form of Creutzfeld-Jakob attibuted to consumption of BSE-contaminated meat.
https://www.nature.com/articles/s41582-021-00488-7
There is some evidence that vCJD could in principle be transmitted via contaminated blood. But people within the UK have donated and received of the order of 50 million units of blood in the decades since the BSE outbreak… and yet as time has passed since we eliminated BSE-contaminated meat from the food chain, the number cases has dropped to zero. (Note that there can be a long incubation period, so the ~3 cases per hear still occurring through ~2011 are almost certainly all still attributable to consumption of contaminated beef decades earlier.)
There is a theoretical risk that blood from an asymptomatic person who ate beef in the U.K. in the 1980s could infect someone with vCJD. The magnitude of that risk is probably similar to the risk of being killed by a meteorite.
It’s more that the disqualifying reason was stupid.
I mean, I suppose I shouldn’t complain - I get the kudos for volunteering without the minor physical inconvenience of actually having them take my burger-tainted blood.