The PM promised, or at least his words implied a promise, back in January that the government would deliver 80,000 vaccinations a week by the end of Feb and would complete 4 million by the end of March.
Any project manager with half a brain contemplates 3 scenarios: best case, worst case and most likely case. Then tactically he or she undertakes to deliver a bit less than ‘most likely’.
Thus if the most likely scenario eventuates, the manager looks good because he/she has over-delivered. An outcome better than ‘most likely’ makes him/her look like a legend.
If the worst case happens, the outcome is only a bit less than promised and there are probably understandable and acceptable reasons for the under-performance. Even so, a good manager will monitor progress and take correction action required to get it back on track.
Only a dolt or amateur would promise the best case scenario. In the unlikely event of it happening, the person responsible doesn’t appear to have done anything special. Even worse, achieving an outcome less than best case, e.g. achieving the most likely outcome, is a significant under-delivery and hints at incompetence and suggests that marketing spin is more important than substance and delivery, completely negating and reversing any PR and reputational benefit gained from the earlier over-optimistic announcement and promise.