From The Lancet article:

The vaccines that are currently available are safe, effective, and save lives. The limited supply of these vaccines will save the most lives if made available to people who are at appreciable risk of serious disease and have not yet received any vaccine. Even if some gain can ultimately be obtained from boosting, it will not outweigh the benefits of providing initial protection to the unvaccinated. If vaccines are deployed where they would do the most good, they could hasten the end of the pandemic by inhibiting further evolution of variants. Indeed, WHO has called for a moratorium on boosting until the benefits of primary vaccination have been made available to more people around the world.18 This is a compelling issue, particularly as the currently available evidence does not show the need for widespread use of booster vaccination in populations that have received an effective primary vaccination regimen.

All I'm getting from this is that they want to stick to focusing on getting everyone initially vaxxed before they push boosters. Not really a smoking gun IMO. Talk of boosters is probably turning off more people from getting initially vaxxed in the first place.