For video editing the productivity gains are mainly in the editing, not in the rendering. Rendering time is more like a performance metric. More responsive editing process, effortless real-time previews - these are the real gains.
For sure but a 10% gain isn't a gain if you already reached your target goal of smoothness.
For example if you can edit at $your_target_resolution and everything is liquid smooth without dropping frames even with a decent amount of effects then any improvement is overkill.
I'm sure for crazy high end set ups (8k video, etc.) an M1 Max would be nice but for other folks editing 1080p or 1440p videos at 30-60 fps you can get liquid smooth editing even with ~5-6 year old hardware that costs $1,000 all-in (a bit more expensive now due to GPU prices being temporarily crazy in price).
