No one knows anything about this rumour beyond it says there is a Codex: The Crimson Slaughter coming, not that its a supplement from the Chaos Space Marine codex, perhaps it will be a new codex that addresses the issues you're raising? Its not worth arguing about at this point.
And fluff-wise, Codex Chaos Space Marines is better for HH-era traitors, remember that Codex: Space Marines represents Space Marines fighting using the dictates of the Codex Astartes, not how they fought as Legions and not how they fight as disparate warbands formed from the shattered remnants of those Legions, look at how Astartes in the Heresy rules fight, giant blobs of dudes! Bikes were only used as Outriders by the Legions, except for the Khan’s White Scars, so command structures wouldn’t have had access to them as often, But hey, use Codex Space Marines if you want, you won’t get any Daemon Princes, possessed, Daemon Engines