Here is how I (judo training, no BJJ training) think of the two presented positions:
Position 1: opponent on knees
The opponent is on their knees, so attacks are limited to their arms. There is no direct line of attack to the groin, so you can defend arm attacks by either disrupting the opponents balance with your legs or attacking the elbows with your feet.
Presumably you will either transition to attack including your arms or create additional separation to get up.
Position 2: opponent standing
At this point I feel vulnerable on the bottom. The opponent is standing, with ability to use both their hands and feet, while on the bottom, there is no contact with the hands. There is danger of the standing opponent disrupting your feet/leg defense with their hands and stomping on your groin with their feet.
In these video situations, the opponent just seems intent on punching you in the head, which is not the problem you have asked about.
With the initiative on the bottom, I would press the opponent off sharply to create separation and come to a standing position.