I think it is OK to double in North.
The explanation is wrong as there can be 6+ hearts like here, when the hand is not strong enough to a forcing 3H
After the D south should bid 3D, and not 3S
After 3S North has a problem and might be 4H, but this is limited to a hand not strong enough to bid 3H the first time so around 10-12.
This means the 5C exclusion is an overbid caused by the wrong definition of 4H.
So this is the correct bidding
Also noticed that 3H is not 5 but 5+ hearts, and limited to 12 hcp
05AD954A4A5EA1CD494785F1A29F
I think it is OK to double in North. The explanation is wrong as there can be 6+ hearts like here, when the hand is not strong enough to a forcing 3H
After the D south should bid 3D, and not 3S
After 3S North has a problem and might be 4H, but this is limited to a hand not strong enough to bid 3H the first time so around 10-12. This means the 5C exclusion is an overbid caused by the wrong definition of 4H.
So this is the correct bidding
Also noticed that 3H is not 5 but 5+ hearts, and limited to 12 hcp