I'm skeptical. The phrase "pacing the frontier" implies disproportionate regulation of firms at the frontier, which if anything would give smaller players time to catch up.
tl;dr
A slowdown that doesn't slow you, that your competitors must also obey, enforced by a government you've asked for an antitrust exemption from, is not a slowdown... it's a moat.
Why do you believe this is what Amodei is calling for? Why would this be a slowdown that "doesn't slow" Anthropic?