This doesn't really prove it.
Running ths game multiple times will do the same, because the pages will stay cached. Operating systems are smart with RAM. Things that were recently used stay in RAM, even though the OS reports it being "free". Read this for some more info: https://www.linuxatemyram.com/
And preload might swallow the filepath arg without doing anything with it.
Instead you could share the output of
preload --help
preload --version
sudo preload --verbose
# followed by running a game
What you describe can actually be done with another tool https://hoytech.com/vmtouch but not with preload.