You’re comparing the football to going cinema. It’s clearly not the same, it’s a poor comparison.
Like I keep saying over and over again, if you feel a fan is being inconsiderate then report it. I just don’t feel the club will act upon a fan leaving their seat then returning to it. I totally understand the OP, however, what do you want to happen? I highly doubt these fans have left the ground because I doubt they would get back in. More likely is they’ve gone down to watch the last few minutes in the screens then returned to their seat. Hardly crime of the century.