There is substantial evidence that the second shot of the Pfizer vaccine is VERY modestly enhanced byt the second shot.
21-28 days after the first shot the average immunity peaks at 91.7%. The average immunity two week post 2nd shot has only increased to 95.2%. Only fractionally better.
Much discussion was given to the premise that emphasis should be removed for the second shot and concentrated on giving many more first shots early. There is validity to that argument.
But is there not also substantial evidence that the 1st shot’s protection starts tailing off after that 3rd-4th week peak? Therefore the 2nd shot to not only restore the better protection, but to convince the body to produce more B cells, which are the ones you really want for extended protection.
The UK formally adopted th policy you discussed (delaying second shots, to front load more first shots).
They got excellent results in controlling the disease and saving lives. One of the best in the world.
I think they wait 12 weeks for the second shot.