They look at the curvature of the ball not the bottom of the ball. If you search for the video on Youtube you will get one where EPL referee Mike Dean explains why it was not a penalty
They should stop this stupidity of showing yellow for removing your shirt. In the emotion you do it. I dont understand what they gain by giving a yellow in that situation
Means it is not where the ball touches the ground but the entire ball has to cross the line you know how for goals even if the ball crosses the line the middle part where it is overhanging is still hanging over the line
The whole of the ball must cross the line for it to be out of play and VAR decided that at least some of it was still overhanging
www.theguardian.com
In the man city liverpool match if this ball was on the ground then also no goal would have been given coz the bottom part crossed the line but the middle part(curvature) was still on the line same with Japan except the curvature here was over the line and still in play