I certainly hope that it does.
When my POTS first became truly problematic I had serious leg pains, my legs would go purple and the pain was so bad it made me cry. I had to sit down immediately, or if that didn’t work I had to lie down, in order to reduce the pain. I see your son lies down too but he appeared, in one episode, not to be able to get up. My thigh’s (quadriceps?) became quite weak at one point and it made it difficult to get up.
I hope you don’t mind me saying but I notice that he doesn’t have socks or shoes on a cool surface and I know that my legs hurt much worse when they are cold (and they are cold even in the height of summer, it’s weird!) so I’d like to ask you to put him in some warm socks (with no pattern, ridges or elastic) and shoes or warm slippers, all the time, to see if that helps.