In general, it’s true that Linux doesn’t need to restart for most updates. However, if you get a power cut right in the middle of an update, that could leave your OS in a really bad state. Therefore, for safety reasons, some distros (apparently including CachyOS) do updates in a ‘safe mode’ on boot, so that if there’s a power cut it just rolls back cleanly.
In short, how exactly distros approach updates differ slightly. A tradeoff between safety and convenience.
In general, it’s true that Linux doesn’t need to restart for most updates. However, if you get a power cut right in the middle of an update, that could leave your OS in a really bad state. Therefore, for safety reasons, some distros (apparently including CachyOS) do updates in a ‘safe mode’ on boot, so that if there’s a power cut it just rolls back cleanly.
In short, how exactly distros approach updates differ slightly. A tradeoff between safety and convenience.