By the time TP has the Tenet organisation set up and the second (unseen) half of the temporal pincer is in place he will have most definitely subscribed to the axiom stating that 'what's happened happened', IMO he has already accepted this by the time the credits roll.
There is nothing to suggest that Fay (his CIA handler on the medical boat) or Barbara (the scientist) were directly recruited by TP. If they were, they do a good job of acting if he were a novice and so the TP's best chance of them not spilling the beans is to avoid his future self coming into contact with either of them. As there is nothing in TP's intelligence work that exposes him to inversion prior to the opera siege (where he first encounters the Pu-241 / 9th section as well as the inverted round Neil uses to save his life) this becomes the ideal place to erm, introduce himself to these concepts for the first time.
While Fay sees the suicide pill as a loyalty test this may be more for his own benefit allowing him to introduce TP to Tenet as somewhere along the line his fellow agents pill has been deliberately replaced with a fake in order for TP to allow himself, retrospectively, to survive the interrogation following the siege.
Remember, it is Sator's goons who are giving him TP go over and as such he has realised that the pincer only worked due to himg hiding all this information from both himself and Sator's orbit until the final 3 - 4 weeks prior to the Talinn tent - pole inversion which is as far into the future as we see, notwithstanding the death of Priya in the final few shots.
If all of this still hurts ones head then it only means that you are human as we are continually dealing with chicken / egg scenarios here.