WTA swing is also inside out lol... any type of seperation so that the ball is away from the body will mean the racquet will swing out away from the body unless you take the racquet back exactly behind the ball before you swing... another st*pid and useless analysis.
It seems youtube is not lacking these.
It is odd that the video really teaches a set of pendular figure-eight motions that remind me more of a good swing in the wooden-racquet era. From my point of view approximately none of the essentials of a so-called ATP forehand are mentioned, and the ATP swing is definitely not a figure-eight pattern in any meaningful way, not for example as a way of determining the racquet's behavior or accumulation of racquet head velocity. Perhaps the figure-eight example is especially beneficial for young beginners?
It seems to me the core of a solid contemporary ATP forehand is this: Power the hitting upper arm via upper body rotation. (Fed, Rafa, and most others keep driving the hitting arm forward with UBR until the hitting arm/shoulder/upper back muscles kick in to pull the hitting hand briskly leftward/forward/upward (for a righty). At that point, just before the strong leftward arc, the racquet head should have so much velocity that the leftward sweep still sees the racquet head moving forward to contact very quickly.
The last motions of the hitting arm before UB rotation starts are usually to pull the upper arm back into tension with the shoulder, then lower the arm (straightening it near the lowest point if you hit straight-arm). For each major current player UB rotation is powered up just as the "pull out" and ESR are about to be initiated....although the pull-out (grip cap leading) is a misnomer: The rotating UB still leads the arm. The pull-out is really a push-out of the grip toward the expected contact point, which does depend on the incoming ball and player's position. The greater the grip push-out is, the larger the ultimate arc will be. For a given time taken, joined to the longer arc, the faster the racquet head speed will be into contact. (Forward "pull" isn't needed, as the UB rotation will force it.) The initial instant of UB rotation provides a safe and easy moment to rotate the upper arm into ESR, catchin the weight of the racquet on the large forearm muscles, which will immediately go into flex. See, e.g. Rafa, Fed, and most others.
The UB rotation can accelerate the heavy upper arm (and lighter forearm...) very quickly, faster than shoulder muscle can, and contains massive momentum once in rotation. ESR and "getting racquet head lag" are, to my mind, the same thing, given the needed initial angle between racquet and forearm at the time of UB rotation launch.
The magic of the ATP forehand lies, I believe, in the extent to which it maximizes the length of arc which the racquet head will travel when it has to make the sweeping left turn to keep up with the leftward moving hand ...while minimizing the time in which the arc is transited, from initial to final point, i.e. contact. The arc is maximized when the grip has been pulled (or pushed, POV) outward toward the expected contact point during the pull-out phase: With the racquet head in lag, the initial point of the arc (for the racquet head) is set well back, and taking the ball out in front determines the arc's maximum terminal point. The velocity of UB rotation leading the swing, plus the power of the leftward pull out/across/up into contact, determines the time taken for the racquet head to traverse the arc. So, contact! But with ISR exactly into the instant of contact to add power and topspin (via both tilt and upward velocity in the plane of the stringbed).
Can't find the figure-eight in that description. Perhaps that's just my foible?