A citation from a Facebook post of his:

1. Something is injured – you might want to change mechanics to protect is while it heals
2. Something is injured – you might want to specifically try to load it to stimulate healing but not too much load (see #1)
3. Performance – alignment, bracing, not bracing, muscle sequencing etc matter for performance. Biomechanics is paramount here in many tasks
4. Temporary desensitization – changing mechanics can be of great help. If it hurts to flex your spine it is definitely cool to teach a neutral spine or adopt a hip hinging posture to keep the person doing the activities they love. This is sold as something that is temporary and they can ease back into doing the aggravating posture over time
5. High load activities – if you are performing a movement that sees some tissues near their threshold of adaptability or ultimate tissue strength then watching the kinematics or kinetics of the movement can matter because you can keep the tissue load under its failure threshold (think ACL load when cutting or landing)
6. Movement preparation – biomechanics matter here because we have to respect the ability of the body to adapt. You can’t just keep hammering the same postures, movement patterns, sports or poses without respecting the finite ability of adaptation and how that ability to adapt will also be influenced by other factors.
7. Habit interruption – sometimes people keep doing the same type of movement and it aggravates them and they don’t even realize it. If they are unable to change their movement pattern to desensitize because of strength, ROM deficits or motor control then those impairments are now relevant impairments and might be worth correcting.