Trapping The Last Exaltationists

The siege of Bactra (see here) was not a world-changing event but Shalten fakes evidence that it could have been and ensures that this evidence is publicized during a year when there is reason to believe that some Exaltationists may have been lurking. If the Exaltationists heed Shalten's spurious evidence and try to change the course of history from 209 B.C., then Patrolmen will be waiting for them.

When the last Exaltationists have been apprehended, Shalten has the spurious evidence deleted from the timeline. This strikes to me as both unnecessary and dangerous. What other events, necessary to the Patrol's plan, might unintentionally be deleted in the process?

Shalten's and Everard's 1987 conversation about the Bactrian letter "now" never occurred. Nevertheless, Everard of course remembers it and it is unnecessary for Shalten to discuss the letter again with Everard in 1902 in order to ensure that he retains the memory. That part of the dialogue definitely makes no sense.

Patrol agents like Shalten have some nuanced way to manipulate events in order to ensure exactly the right combination of the preservation of the preferred timeline with deletion of potentially harmful happenings but we are told very little of how they do it.