It's not like healthcare provide and pharmacists aren't busy enough already, now they have to keep track who gets what dose:
https://www.reuters.com/article/us-health-coronavirus-usa-moderna/u-s-may-cut-some-moderna-vaccine-doses-in-half-to-speed-rollout-official-says-idUSKBN2980NW
Also, it's not going to help people's reluctance to take a vaccine if your telling them you're only going to give them half the recommended dose (even if it works or not).
https://www.reuters.com/article/us-health-coronavirus-usa-moderna/u-s-may-cut-some-moderna-vaccine-doses-in-half-to-speed-rollout-official-says-idUSKBN2980NW
Also, it's not going to help people's reluctance to take a vaccine if your telling them you're only going to give them half the recommended dose (even if it works or not).