It's true that lack of mobility can limit power.
In regards to the video, it's hard to say. He's a bit annoying with his presentation huh? Looks like he's a crossfit dude and a chiropractor, which is always a concern lol.
I can't really fault his introduction that much, although it's a bit all over the place and connecting dots that maybe doesn't have to be connected. The title also says it'll help you with hip impingement, but then he mostly talks about lack of extension and hip stride. It is true that there is a tad internal rotation during a stride, but it's very little and often times not the limiting factor.
In regards to the exercises, I like stretching out the adductors and hamstrings. Although you wont get the entirety of the hamstrings doing what he's doing. Semitendinosus and semimembranosus (part of the hamstrings) are somewhat attached to adductor magnus (important adductor muscle), but biceps femoris is not (other part of the hamstrings). Adductor magnus is a very interesting muscle as it both externally rotates the hips, adducts it and extends it! It's often very tight. Anyway!
I don't completely understand the rational of trying to pull the head of the femur anteriorly, or forward, in the joint capsule if you have hip impingement or lack internal rotation. For extension it makes sense, but again that's why his vid is a little all over the place. It might help to loosen it up independent of direction, but the underlying issue with hip impingement is that the anterior structures are being compromised. You would want to mobilise the head posteriorly, or back, to alleviate and improve internal rotation. It's always hard to say what effect certain exercises will have on you specificly and your pain, as it depends on a lot of things including the root cause, but what he's doing doesn't make a lot of sense.
Anyway TS. Where exactly is your pain? During/after which activies does it become worse? In which ranges of motion are you limited in, do you know? Have you been to a physio or other health practicioner? Also, which exercises are you doing now 5 days a week?
