In 'Reacher' Season 3, a big portion of the story is all about Reacher seeking vengeance against a guy named Quinn for something that happened while Reacher was still in the active military.
In the flashback episode 'Dominique' of 'Reacher' Season 3, a major change was made to the original book, Persuader, by altering the romantic relationship between Reacher and Kohl.
By making Reacher and Kohl's relationship platonic and friendly, rather than romantic, the show avoided a tired cliché of a romantic partner being brutally killed.
This change in Reacher Season 3 makes the flashback episode clearer and eliminates the old action trope of a killed romantic interest.