Cable lengths matching does not matter on a house scale. On a 12AWG wire you are in great shape. Volt drop will not be an issue. As for snake oil theory, belden measures wave propogation in cables with reference to the speed of light. Really fast stuff. Properly sized, 15ft vs 100ft of spkr cable doesnt matter at all.
When I throw the main switch in a massive warehouse all the lights strike at the exact same time.
Electron flow is virtually instantaneous.
In my room I ran 2 conduit to ensure flixibility for later. Exact same 2" vac line. Great stuff and cheap. Welcome to the madness that is building an AV space.