Neither of these points are quite correct - mRNA vaccines were extensively used for both initial vaccinations and boosters in the UK. IIRC the AZ vaccine was quite quickly withdrawn for everyone under 40.

Minor thing, but that'll probably be expanded to include Novavax in a relatively short amount of time. Not that it matters much for the progression of the pandemic (it's far too late to make a big difference, and will only mop up a few vaccine hesitant people).

Not true, Pfizer was used in the initial vaccination rollout too.

Huh? Plenty of previous non-covid vaccines require more than two shots.

I suspect they did their own research

What? More than two doses is extremely common for vaccines. See e.g. https://www.cdc.gov/vaccines/schedules/hcp/imz/child-adolesc...

Infants have three or four doses for some of their vaccines.

Utter nonsense. A lot of vaccines need multiple shots -- independent of the duration of the protection.