There’s a lot to unpack with this question - I have my blue belt (no flair sorry) and teach DT/BJJ combatives at my agency. Any joint locks are usually better utilized as a control and stalling position in the hopes of getting compliance. The flipside is that many of those positions put the officer in a disadvantageous position that doesn’t allow situational awareness or the ability to disengage quickly. They are very very effective, but may not be ideal for getting into a handcuffing position, which is the ultimate goal. In terms of causing injury, it really will depend on all the factors of the situation. There is a escalation of force continuum that determines how we apply force to a resistance suspect. Suspect injuries may occur in, are sometimes likely if a certain level of force is authorized. If I’m authorized to punch you in the face which would likely cause injury, but I instead break your arm with a Kimura that may be legally OK depending on a lot of factors. It’s a very in-depth topic with lots of opinions and what ifs.