Why do people trying to advocate against the movement push the narrative that source code is being asked for or that it is the only solution to make games work after it is sunset?

Just put in an offline mode like was done for Redfall. https://www.ign.com/articles/redfalls-final-update-is-live-bringing-with-it-offline-mode-dlss-3-and-more

Knockout City provided tools for gamers to run their own private servers after it shutdown

https://www.knockoutcity.com/private-server-edition

Suicide Squad Kill the Justice League has servers still running but put in an update to provide offline mode

https://dcgamessupport.wbgames.com/hc/en-us/articles/36119520746515-Suicide-Squad-Kill-the-Justice-League-Offline-Mode-FAQ

And fans have picked up the slack in Hitman with the peacock project when the companies lock certain things to online.

To reimplement the server side part of Hitman to run locally. So that if/when the official servers go down, anyone can still play the game. They've also made it easier/better to mod the game in various ways.

This includes leaderboards, contracts, game progression and unlocks, bonus/event missions, as well as being able to play elusive targets with scoring. All things that are unavailable when you play offline

https://old.reddit.com/r/HiTMAN/comments/12o76t3/what_is_the_purpose_of_peacock_project_mod/

So that's what I'm guessing the movement wants. Just to leave the game in a playable state as opposed to inaccessible when servers go down. And source code wasn't provided for these solutions.