From what I've read these reshoots are all originally planned and him shooting them was always the plan because his company have been doing the stunt work from the start.
100% correct this is pretty normal procedure and welcome these additional scenes
article I found earlier that I couldn’t have said better myself
'John Wick' director Chad Stahelski will design new action sequences for Cathy Yan's film, and his experience suggests he will be supporting her narrative, not meddling with it.
www.hollywoodreporter.com
“'John Wick' director Chad Stahelski will design new action sequences for Cathy Yan's film, and his experience suggests he will be supporting her narrative, not meddling with it.
The Birds of Prey are cranking up the action. Last week, The Hollywood Reporter learned that Cathy Yan’s upcoming DC Comics adaptation Birds of Prey (And the Fantabulous Emancipation of One Harley Quinn) will
receive some backupfrom John Wick trilogy director Chad Stahelski. Stahelski’s stunt company, 87 Eleven, has been working on the film since production began. As additional photography gets under way, the stunt coordinator and filmmaker will be joining the crew in an uncredited role as second-unit director to craft more action scenes for the film. While fans have been waiting for the first trailer to finally see Harley Quinn (Margot Robbie), Huntress (Mary Elizabeth Winstead), Black Canary (Jurnee Smollett-Bell), Renee Montoya (Rosie Perez), and Cassandra Cain (Ella Jay Basco) in action, the long wait for footage may be because Warner Bros. wants to showcase the film’s stylish action set pieces in order to make a strong first impression. While there’s been some reservations expressed on social media, an uptick in fight scenes for an R-rated, street-level superhero movie can only be a good thing.
Of course, news of reshoots are often met with concern, despite them being a standard part of most major studio productions.
The biggest movie of all-time, Avengers: Endgame, had two sessions of reshoots scheduled in fall of 2018 and spring of 2019 and no one batted an eye. No doubt, some level of that reshoot concern stems from how Warner Bros. handled
Suicide Squad (2016) and Justice League (2017), resulting in very different final cuts than what were initially marketed. But things have changed at Warner Bros since then, and studio restructuring has led to some transitions of power that are promising to avoid the missteps of before. While there is perhaps some amount of trust yet to be earned from the studio when it comes to their DC properties, that is, if the successful directorial visions of Aquaman (2018) and Shazam (2019) weren’t enough, Birds of Preyappears to be in safe and capable hands.”