I'm not a psychology researcher, but my guess would be that the nature of it being a time-limited puzzle game where you have to juggle multiple factors means that your short-term memory gets filled and the traumatic images are "dumped" in favor of remembering how many times to rotate the L piece. "As soon as possible" is probably because the sooner you do it, the less likely it is to become part of your long-term memory.
If that is true, then other time-limited activities where you have to remember and plan in a tight time frame may serve a similar purpose.
This can have an effect hours after the traumatic event happens too! All participants were treated within about 6 hours and played for a total of 20 minutes of Tetris (with at least one play time of 10 minutes straight).
Here are the links given in the screenshot:
Tetris has been proposed as a preventive intervention to reduce intrusive memories of a traumatic event. However, no neuroimaging study has
A single dose psychological intervention, which includes using the computer game Tetris, can prevent the unpleasant, intrusive memories that
Here is the paper that the second link uses as a source:
After psychological trauma, recurrent intrusive visual memories may be distressing and disruptive. Preventive interventions post trauma are
