I found this interview by CBC to have a good amount of detail, see around 8:00 for your question
https://m.youtube.com/watch?v=Y7gbMJCW2xY
Reasonable force doesn't mean planning it out perfectly in a stressful situation. It means doing what a reasonable person would do in your shoes.
- someone comes at you with a knife and it looks like they'll hurt you -> deadly force is more warranted
- someone is standing back while holding a wrench and telling you not to come closer -> deadly force is not as warranted
Like the video describes, there's still lots to this case that we don't know and to me it doesn't seem like this is setting any new precedent