That is a lot of knowledge that isn't anything to do with this decision, though.
All the experts - here and abroad - agree that the best time to give people the second dose of Pfizer is 21 days after the first dose. This decision is not about how the virus works, or how its best treated in a patient, its about wider social issues - so that they can give more people partial protection via the first dose (edit) and thereby start to control an outbreak.
For that, there is no evidence as to give them an idea whether it will work - certainly not for this particular vaccine and I am not even sure its ever been tried with any other vaccination programme on this scale (in the sense of knowingly giving weaker protection to individuals so that you can you can spread what doses you have to more individuals).
It is a guess; whether people think that is a guess worth making in these circumstances and given what the alternative was, is up to them. Personally I hope it works, but if it doesn't there should be extremely serious questions asked.