Vallan,
As Max stated, the most integral part of PMTS is tipping. Tipping does not simply mean putting the skis on edge. Rather it is very specific in HOW you put the skis on edge. PMTS teaches that you tip the skis on edge with your feet, and always lead that tipping effort with the inside ski tipping to it's little toe edge or 'LTE'. In order to successfully accomplish this movement, it is imperative that the skier is balanced on the big toe edge or 'BTE' of the stance [weighted] ski. I've pulled some stills from junior's skiing for you to take a look at with us.
In this initial frame we already see that tipping is not happening with the feet, but rather the skier is employing a 'hip dump' to edge his skis. 'Hip dump' implies that the hips are being dropped into the turn while the skier is supported by the inside ski. This pulls the pressure off the stance ski, and little turning actually occurs. Here the outside ski is very edged, while the inside ski is flat - no real balance on the BTE at this point and no LTE tipping.
Again, more of the same as outlined above, just further into the turn here, with a slightly visible stem.
In this second turn, we can see excessive scissoring/directing of the inside ski while it is completely flat, at the same time that the outside ski is tipped onto a high edge. This is not tipping as PMTS defines it.
This image is a few frames later, and the skier is still not showing matching edge angles; a sign that there is no tipping to the LTE. Directing of the inside ski is still present.
Again, same as above.
A few frames later, the edge angles are closer to matching, but only after the inside ski has been stood on (while mostly flat) for nearly the entire turn.
The above statement is evidenced by observing the ski tracks in this frame - specifically the inside as I've pointed out.
Immediately we jump to the next turn where it is more of the same - big toe edge dominant skiing created by dropping the hips into the turn.
Here, he has come closer to matching angles earlier in the turn (likely due to higher speeds), but we still see that the outside ski is at a higher edge angle than the inside ski.
Here we see a huge hip-dump. The inside ski is entirely supporting the skier's mass. The outside ski is doing nothing at this point in the turn.
Lastly, aside from the obvious balance issues that hip dumping causes, I'd like to use this frame to point out the fore/aft problems that can occur from hip dumping. Here around the apex of a turn, or just slightly past, we see the skier very far behind the skis. This can only be corrected by establishing balance on the stance ski AND pulling and holding the feet back. Additional video, perhaps of the skier not performing a drill, would help us to better assess the fore/aft nature of his skiing.
Tipping and balance is the most important focus for his skiing right now, as lack of tipping will hold him back as he grows. Read through Essentials and work on all of the Tipping progressions. Isolate the foot/ankle movements and make sure he understands the difference between putting his skis on edge with his feet versus putting his skis on edge with his hips. All that said, this little guy is skiing very well for a 7 year old - you should be pleased.
Discipline is the refining fire by which talent becomes ability.
www.youtube.com/c/heluvaskier
and to get some feedback on both good movement and movements that needs more improvement. 
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