Surely, if enough testing had been done, those that nearly died,...

Surely, if enough testing had been done, those that nearly died, would not have had to be resuscitated.
I think this is overstating facts @Kerrybrad

According to the article posted:
Two people who were jabbed with Pfizer’s recently-approved coronavirus vaccine in the UK had to be treated for serious adverse reactions — leading to warnings that those with “significant” allergies may not be able to get it. The unidentified duo — both staff in the UK’s National Health Service (NHS) — needed treatment for an “anaphylactoid reaction” Tuesday after they were among the first in the world to get the shot. They both had serious reactions, but recovered after treatment, the NHS said. The pair both had a history of allergic responses, and each carried an adrenaline shot — sometimes called EpiPens — used to save people from potentially fatal reactions.

Sounds to me they received their EpiPens and maybe supportive therapy until well. There is no mention of them having to be resuscitated.
The request for resuscitation equipment on hand is a very cautious response, as it should be as the incidence of this side effect is yet to be established and could be fatal in some circumstances.

It is also common for side effects to be recorded after drugs that have had extensive research are introduced to the market. I have fill out many a 'green card' over the years reporting side effects. There are two choices here. Do more testing to get a greater understanding of the side effect profile, or try and save some lives. I know which one I prefer.